I did the same. I went straight to the Alexandrian Hypothesis and then read through the whole bookl afterward. I've been pretty interested in Alexandria's role in both the bible OT and NT writing periods. There was a guy posting here a while back who was convinced that the Septuagint is the original bible and that any Hebrew version was written later. Technically it's the oldest extant version, but even still it seems odd at first to think that there was no Hebrew bible any earlier that was eventually translated to Greek. But he was convinced that the Greek was the original. He offered no elaborate Septuagint Priority Hypthosis (SPH) in the clear terms that you have provided in video, but it was a hell of an insight on his part nontheless.
You struck another nerve with me when you brought up Berossos in the video series. Years ago I read through Campbell talking about an interesting discovery he'd stumbled into while comparing mythologies. He was pointing out that there's evidence from the bible itself which reveals how the older Babylonian and Vedic based flood myths were used in order to come up with the biblical account:
"The Inner Reaches of Outer Space: Metaphor as Myth and as Religion"
"For example, in the Hindu sacred epics...the number of years reckoned to the present cycle of time, the so-called Kali Yuga, is 432,000; the number reckoned to the "great cycle", within this Yuga falls is 4,320,000. But then reading one day in the Icelandic Eddas, I discovered that in Othin's warrior hall, there were 540 doors, through each of which, on the "Day of The Wolf" (that is to say at the end of the present cycle of time), there would pass 800 divine warriors to engage the antigods in a mutual battle of annihilation. 800 x 540 = 432,000.
...In Babylon, I then recalled, there had been a Chaldean priest, Berossos, who c. 280 BCE., had rendered into Greek an account of the history and mythology of Babylonia, wherein it was told that between the rise of the first city, Kish, and the coming of the Babylonian mythological flood (from which that of the bible is taken), there elapsed 432,000 years, during which antediluvian era, ten kings reigned. Very long lives! Longer even than Methuselah's (Genesis 5:27), which had been of 969.
So I turned to the Old Testament (Genesis 5) and counting the number of antediluvian patriarchs, Adam to Noah, discovered, of course, that they were ten. How many years? Adam was 130 years old when he begat Seth, who was 105 when he begat Enosh, and so on, to Noah, who was 600 years old when the flood came: to a grand total, from the first day of Adams creation to the first drop of rain of Noah's flood, of 1,656 years. Any relation to 432,000? ...it was shown that in 1,656 years there are 86,400 seven-day weeks. 86,400 divided by 2 equals 43,200.
And so it appears that in the book of Genesis there are two contrary theologies represented in relation to the deluge. One is the old tribal, popular tale of a willful, personal creator god, who saw that "the wickedness of man was great in the earth..." (Genesis 5:6-7). The other idea, which is in fundamental contrast, is that of the disguised number, 86,400, which is a deeply hidden reference to the Gentile, Sumero-Babylonian, mathmatical cosmology of ever-revolving cycles of impersonal time, with whole universes and their populations coming into being, flowering for a season of 43,200 (432,000 or 4,320,000) years, dissolving back into the cosmic mother-sea to rest for an equal amount of years before returning, and so again, and again, and again.
It is to be noticed, by the way, that 1+6+5+6=18, which is twice 9, while 4+3+2=9: 9 being associated with the goddess mother of the world and it's gods. In India the number of recited names in a litany of this goddess is 108. 1+0+8= 9, while 108 X 4 = 432.
...It is strange that in our history books the discovery of the precession of the equinoxes should be attributed to Hipparchus, second century BC., when the magic number 432 (which when multiplied by 60 produces 25,920) was already employed in the reckoning of major cycles of time before that century.
I recalled this immediately while watching your videos establishing the SPH. It's all right there in the OT plain as day. And it makes so much sense too. All together it looks like the Greeks pressed the Jews for a mythology and they responded by getting into the records @ Alexandria and pulling from a variety of myths ranging from the near east to far east. The Brahma / Abram and Saraiswati / Sarai stands out especially. But as stated above it really looks like some writers sat down and came up with the Patriachal lineage from reading through Berossos. And you're SPH is basically an extension and an advancement to what Campbell stumbled across by chance.