I agree with pretty much almost all of your interpretation of part 8. You leave a fair amount of it open to future conformation or elaboration, which, IMO, is good, although I think my interpretation is, perhaps, a little more open than yours. (Maybe that just means I’m lazier.)
And this is quite good: “What we’re seeing here is essentially a creation story, but in this case it’s the creation of the crack both in our reality and in the soul of modern humanity.” I quite agree.
You’re analogy of the girl & boy to Adam & Eve is, IMO, original and worthy of consideration.
“what the hell does any of this really have to do with Twin Peaks?” I’d say (and I’m aware you’re referring to the town of Twin Peaks): Everything.
Finally, I consider the episode (the entire series, actually, but especially part 8) to be a work of art to be enjoyed with full attention, as one would enjoy any work of art — a music concert, or viewing of a painting or sculpture, or etc. The more attention you give to it and the more you open to it, the more appreciation and enjoyment you discover. I watched it a second time a few days ago and it haunts me — not all the time — but now and then I just recall parts of the episode and think “Wow, amazing” or “Wonderful”. Especially, I often can’t (and don’t want to) get the scene out of my mind in which Senorita Dido sits in the “lounge” (room in the White Lodge, or whatever) listening to that haunting, vamping (yet subtly/irregularly shifting, which makes it even more haunting) jazz sequence. It’s strange and yet completely appropriate (again, IMO) for the context and surroundings. The same sequence may have been repeating for days, months, years — who knows? And I’m sure Ms Dido will never get bored of it. (Since, unlike what Windom Earle thinks, there’s no such thing as boredom in the white lodge.) There aren’t many TV shows or movies that I feel are worthy of my 100% attention. (Perhaps “Better Call Saul” is another example, though it doesn’t grab my attention the way TP does.)