I don't see the 42 districts of Egypt in documents known in the 15th century. What I find is Diodorus's report that Typhon hacked Osiris's body into 26 pieces, and Isis buried one in each district of Egypt, along with Plutarch's report that the Egyptian alphabet had 26 letters. So there would be a correspondence between districts and letters of the alphabet, at 26 rather than 22. And since they knew about the 36 decans (at the Schifanoia and elsewhere), they may have known to identify them as the gods of Egypt's districts. That is not 22 or 42 either. Graves, who usually uses sources available in the Renaissance, has 12 districts for the delta; he gives no reference for that number, however, and doesn't mention Upper Egypt.
Checking Graves' Greek Myths, I see that what you write about the parallels between the Theseus myth and the Achilles myth is in fact in sources known in the late 15th century: Plutarch's Lives for Theseus; the Iliad and Euripides' Hecuba for Achilles; Pietro da Montagnana, d. 1478, had translated the latter in Padua (Wilson, From Byzantium to Italy, p. 115). There was also Seneca's version, the Troades; it was at least in Latin. In these plays Achilles does indeed get Polyxena after death, sacrificed on his grave. I still can't find Achilles getting Helen, too; instead I find him getting Medea, in one variant; but that seems like a small point. I don't see the Theseus myth in any of the early tarot. I see Dionysus, as you know, and there are many parallels between the two myths; but I don't see Theseus specifically. Theseus never made it to godhood, despite the Athenians' best efforts (per Graves) after the Persian Wars; so he never had his own cult. As a result, the Renaissance humanists of the 15th century (Pletho, Bessarion, Ficino, Pico, Politiano, etc.) are fascinated by Dionysus, but not Theseus.
Joseph Campbell did a study of orally transmitted myths from around the world and decided that there was one universal "monomyth," which he called "the hero's journey." In describing that myth he was rather selective, both in the myths he chose and the parts he chose to include. (Achilles is not in his index, for example.) The result looks very much like a syncretist combination of Christianity and Hinduism, in fact reflecting his own orientation: Roman Catholicism in his own childhood, Hinduism learned in his early studies and later in life with Hans Zimmer (see Wikipedia on Joseph Campbell). To that mix we might add "the American dream," i.e. that heroes are made and not born: what determines a hero is not who his parents are but rather the journey he takes. Campbell's syncretism is a 20th century version of Pico's, in which the rationalizing under-structure is not the "prisca philosophia" but something like Jungian psychology. (Jung, however, was somewhat different, at least after he got over his flirtation with the Nazis.) Campbell does not refer to your German sources, but he may have known them; he learned German studying in Germany and had contact with many German-language scholars of mythology.
Campbell's "hero's journey" was picked up by George Lukas, who popularized his own reading of it after the success of "Star Wars." His touting of Campbell prompted the Disney organization to develop a sequence of steps--I don't recall how many there were--that all scripts submitted to them had to conform to. Other studios picked up on this and now all scripts have to conform, and film schools in the US teach it as dogma. So Hollywood is today's equivalent of your rhapsodists. The purpose is in Hollywood's case, and to a degree that of the oral cultures, is indoctrination into a set of values in which success is measured by the degree to which one fights for good against evil, i.e. us against them, transforming and "maturing" in the process. That is very far from Campbell's teachings. For him, the hero's victory is in seeing that us and them are the same; he refers to Cusa's principle of the "coincidence of opposites." The rhapsodists can usually be read in several ways.
I don't see Hollywood's version of the "hero's journey" in the tarot trumps. But I do see something like Campbell's or Jung's. The same structure can be found in the myths of Dionysus and Theseus (if we include the journeys to the underworld, which correspond to the "Devil" and "Tower" cards), as well as in the life of Jesus and the "imitatio Christi" by mortals. It is simply the road to Christian, or whatever, salvation.
I expect that the monomyth of the "hero's journey" has been discussed at length in relation to the historical tarot trumps, some for and some against. In the context of cartomancy, it requires some adjustment (otherwise, every reading drawing high trumps would be highly favorable to the querant, in either this world or the next). But in the context of tarot as an educational game requiring memorization of the trump sequence, it works fine.
Many tarot theorists, exemplified by the "Pythagorean tarot" site, apply the same monomyth to the pip cards (see e.g.http://www.cs.utk.edu/~mclennan/BA/PT/VdN.html). They do that by distorting Neopythagoreanism to fit the model; the worst offense is changing the account of 5, making it (instead of 7) the number of crisis.
In the SB at least, I do not see the "hero's journey" model as fitting the pips, except at the end (7-9), the part of the Theology dealing with human beings and Zeus vs. Kronos. The Pythagoreans, like Hesiod, had as their foundation a myth about the creation and structure of the universe, and that's what we get in the SB pips. First came God, then unformed matter, then enformed matter, then the full development of the nonliving world, then plants ("vegetative soul"), then animals ("locomotive soul"), then human beings ("rational soul"), with a resulting crisis. That takes us up to 7. Then 8, 9, and 10 are about the fixed stars (fate), heaven (the resolution of the crisis), and the totality.
In "On the Creation," Philo of Alexandria explicitly applied the Pythagorean model to Book One of Genesis (in Loeb series vol. 1). Up to 7, it fits pretty well, except that Genesis leaves out plants as a separate stage/day. The result is that humanity gets created in the 6th stage/day instead of the 7th. Then Philo gives a Pythagorean account of the 7th day. I have not found any place where he talks about 8 and 9, but then some of his writings are missing. He applies Pythagorean teachings about the 10 in his essay "The Decalogue" (in Vol. VII of the Loeb series). He does not attempt a Pythagorean analysis of the individual commandments, but he does expound at length on why 10 is the appropriate number. Since 10 is the Tetrakys, perhaps what he says is the public part of why the Pythagoreans held the Tetrakys to be divine.
Philo lived 40 or 50 years before Nichomachus of Geresa, and in the same general area. According to Wikipedia, Neopythagoreanism started in the first century b.c.e. The Theology of Arithmetic (4th century) is more developed than Philo (or Nichomachus, as much as we know) and closer to what we see in 10th century Provence. In saying that Kabbalah evolved from Neopythagoreanism, I meant that it evolved in interaction with Neopythagoreanism, and I meant the doctrine of the 10 sefiroth--including the characterization of each one: not the Sefer Yetsirah, but the so-called "merkabah" tradition. Also, I did not mean to say that the "meditation on the 10" didn't exist earlier. Pythagoras may well have gotten it, in part, from Egypt. Egypt had a 10 day week, for example. The Egyptian reverence for 10 may have inspired 10 as the number of commandments, as well as other more esoteric Jewish doctrines later (e.g. the "merkabah" tradition, during the Babylonian captivity), which would have become more explicit and philosophical after the founding of Alexandria. (Another example is the 70 translators of the Septuagint: 7 x 10, the product of the two numbers of completion.) But a definite assertion of influence can be made only starting with Philo.
Now I will get to the I Ching and the mathematical parallels to Pythagorianism involving binary notation. After re-reading Philo, I am a little less skeptical. I said I would have to see 4096's relationship to the Tetrakys mentioned in the Pythagorean writings before I saw its relevance. Well, Philo does mention it--but in connection with the 7--the day God rested--rather than the 10 or the sequence 1,2,3,4. I give the whole section, although the number does not appear until the end:
That is all Philo has to say about "the 7 outside the number 10"; the next section deals with "the 7 inside the number 10," where of course we won't see any numbers above 10.XXX. Now, when the whole world had been brought to completion in accordance with the properties of six, a perfect number, the Father invested with dignity the seventh day which comes next, extolling it it and pronouncing it holy; for it is the festival, not of a single city or country, but of the universe, and it alone strictly deserves to be called "public" as belonging to all people and the birthday of the world. I doubt whether anyone could adequately celebrate the properties of the number 7, for they are beyond all words. Yet the fact that it is more wondrous than all that is said about it is no reason for maintaining silence regarding it. Nay, we must make a brave attempt to bring out at least all that is within the compass of our understandings, even if it it be impossible to bring out all or even the most essential points. Now, 7 or 7th is a term used in two different senses. There is the 7 inside the number 10. This consists of 7 units, and is determined by the sevenfold repetition of the unit. There is the 7 outside the number 10. This is number starting throughout from the number 1 and formed by doubling it and going on doubling (7 times) or trebling, or multiplying by any other number in regular progression; as, for example, the number 64 is the product of doubling from 1 onwards, and the number 729 that of trebling. Each of these forms claims more than casual notice. The second form, clearly has a very manifest superiority. For invariably the 7th term of any regular progression, starting from unity and with a ratio of 2,3, or any other number, is both a cube and a square, embracing both forms, that of the incorporeal and that of the corporeal substance, the form of the incorporeal answering to the surface which is formed by squares, that of the corporeal answering to the solid which is formed by cubes. The plainest evidence of this are the numbers already mentioned: for instance, the 7th from 1 reached by going on doubling, i.e. 64, is a square, being 8 times 8, and a cube, being 4 times 4, again multiplied by 4: and again the 7th from 1 reached by progressive trebling, 729, is a square, being the product of 27 multiplied by itself, and the cube of 9, i.e. 9 times 9, again multiplied by 9. And invariably if one takes the 7th number for his starting-point instead of the unit, and multiplies in corresponding fashion up to a (fresh) 7th, he is sure to find the product both a cube and a square; for instance starting from 64 the number formed by continuous doubling will give us seventh 4096. This is at once a square and a cube--a square with 64 as its side and a cube with 16. (Philo, "On the Creation" XXX, in Loeb series vol. 1)
Philo may have chosen the example of doubling, which gives the result 4096, because it is the simplest illustration of his number-theoretical point. But there might be some other context to which he is alluding, or which makes this example come readily to his mind. That context may simply have been the Egyptian system of measuring volume (and also European, still used in the US: an ounce is 1/8 of a cup; a cup is 1/2 of a pint; a pint is 1/2 of a quart; a quart is 1/4 of a gallon). Or maybe something else.