As far as Agrippa, it does seem that he knows something of him, as is evident on the next page after the one you cite, on which Etteilla calls him a sophist with a very shallow knowledge of numbers. Agrippa had already been translated into French, 1727: https://www.worldcat.org/title/philosop ... ef_results
I have found where Etteilla talks about 5 and 6: it is in a footnote on p. 19 of the First Cahier (http://gallica.bnf.fr/ark:/12148/bpt6k6 ... angEN.zoom). He says:
This is quite in harmony with Christianized Pythagoreanism. He makes no attempt to apply these ideas to the cards, however. The only relationship I see is that Etteilla applies the idea of the 6 days of creation to the cards, with the 6th day that in which creation is completed or perfected. (The word "parfectus" in Latin means "complete" as well as "perfect"; see https://en.wiktionary.org/wiki/perfectus#Latin).Que ceux que veulent écrire la Haute Science des nombres, entendent bien, que chaque nombre a sa propriété comme sa valeur; que supposé: 5 est la sacrée, embrassant l'Universe par l'appui de l'unité & étant placé entre l'Universe 4 et la perfection 6...&c. La propriété connue donne les effets physiques.
(Let those who wish to write the High Science of Numbers, understand that each number has its property as its value; that supposed: 5 is the sacred, embracing the Universe by the support of the Unity and being placed between the Universe 4 and Perfection 6 ... & c. The property known gives its physical effects.
Then again, footnote p. 30 (http://gallica.bnf.fr/ark:/12148/bpt6k6 ... angEN.zoom) he repeats what he has said for 1, 2, 5, and 6 but gives for 3, "3 principles: sulphur, salt and mercury", and 4 is the 4 elements, as well as his preferred (au mieux) "Universe". He then has 7 as "science et sagesse humane" - knowledge and human wisdom. This is in accord with the Theologumena, which gives this number to Athena. 8 is then "multiplication, etendu" (multiplication, extension) and 9 "perfection des hommes simplement, suivant nature" (perfection of man simply, following nature), 10 "sceau divin" (divine seal), i.e. the completion of a cycle, 11 discord et defectuosité (discord and defect), 12 "appel et réunion" (call and reunion). He adds on p. 41 that 10 is the divine circle, 12 the human circle, and 11 the gap between them--i.e. defect, sin (this last p. 58, citing Augustine). That is nice to know, but how it relates to the tarot he doesn't say. Then 13 is the sign of destruction and death, he adds (p. 41). Oddly enough, his Death card is 17, the number that Ross said was the number of Death in Italy.
I have also found where Etteilla speaks of the tarot in terms of 1, 4, and 7, on p. 21 and following of his work just cited and often thereafter. It is not a division into groups of those numbers of cards, but rather of different ways of dividing all 78: taken as a whole (1), in four parts (12, 5, 5, 56) and seven parts (not yet explained). Notice here that the Fool is included as number 22. He explicitly says that the Fool is just after the World in the sequence--despite the numbers "78" and "0" on the card. Given the rather arbitrary division of the 10 last tarots into two groups of 5 (Death is the divider, but the high side is not about the afterlife), I would expect that there is some particular reason for 4. I am not sure about the division into 7 groups. Perhaps he means (7x3) + 14x4), for 3 + 4 groups. That would appear to leave out the Fool. But on p. 38 he gives that card the number 0, or maybe O: it has no number.
It seems to me that one could divide the 22 into groups of 1, 4, 7, and 10 in his conception of the cards: 1 for the Etteilla/Consultant; 4 for the cardinal virtues (cards 9-12), 7 for the days of creation (cards 2-8), and 10 for the rest, including the Fool. But I have not found where he says that in so many words.
That is in general the problem with Etteilla. He uses Pythagoreanism in his books, but how it fits his cards remains a mystery. My view is that his books reflect the intellectual sentiments of his time; but the cards are something else. Their very lack of rationale gives them an air of authenticity--if not as far back as ancient Egypt, at least further back than him.
He is well aware that the sum of the first 12 numbers equals 78, and that the sum of the first 6 equals 21 (p.35) Their difference is 57, a number he has some difficulty interpreting. 56 is easier: for Augustine it was the sign of tribulation (p. 59). How that differentiates the suit cards from some of the 21 he does not say.