Several matters you touch on in the two posts above have long fascinated me.
This section of Genesis you refer to for a start, as it is plain that a number of "hands" have been involved in editing this story, and redacting it, actions we see a good number of times in Genesis, as with every other Bible Book of course, but Genesis is a bit of a mess, it could have done with a proper Editor with a keen eye to tidy it up ! I'm glad there was not, as we can clearly see where interpolations have been made, and where thinly disguised clues are that show the continuing influence of Canaanite religion, including child sacrifice, which continued probably almost up to the Babylonian Exile perhaps, or even longer ?? (I really must read Prof. Stavrakopoulou's Book on this in the time of Manasseh. ).
It is easy too to actually see the clumsy Interpolations, as in this passage, and with the Flood Story etc.
On the matter of the beliefs of the various Gnostic Christians, we have a distinct lack of material, no doubt a lot destroyed by the "orthodox" group who prevailed as the main Christian group.
I hope maybe someone else will comment on this Thread with more info. on these fascinating things