In my opinion, you lay out some pretty good thoughts. I think, though, that you are mostly concerned with the role a certain kind of mystical experience (perhaps most often interpreted as an experience of deity) has had to do with the origin of religions. Please correct me if I am wrong.
That experience -- or at least its interpretations -- seems to vary a bit from culture to culture, and from individual to individual, but I agree with you that there also seems to be something of a core experience. At least, we can look at the various experiences, see commonalities between them, and count those as the core experience. Whether anyone ever actually has a pure core experience is an interesting question.
Years ago, I was rather eager to find commonalities between these experiences. Today I am still struck by the commonalities, but I am also much less likely to discount or gloss over the differences.
I have also become aware over the years that religions, apparently, have more than one root. I believe the first is the mystical experience that I think you're talking about. But there is also a growing body of science concerning a second root. Namely, the origin of religion in such things as agent detection, etiology, Theory of Mind, and other natural functions of our brains. From what I gather, there might be up to twenty or thirty such functions which, each and jointly, help to predispose us to religiosity of one sort or another. The important thing here to recognize about that second root of religiosity is that it is essentially non-mystical.
In bringing up these two roots of religion, I by no means want to neglect things that, while not at the roots of religion, nevertheless shape the religions we have: Things like social factors, economic factors, etc.
If you have access to a library that has this book, or are so inclined as to order one if you're intrigued by early Christianity, Elaine Pagels who is a professor of religion at Princeton wrote a book some time ago called The Gnostic Gospels. What is particularly revealing in this work of hers which broke the ground of this to the public mind, is how in the early Christian movement it was not some single idea that got spread out from a single source as a whole cohesive body of teachings, which then later "heresies" crept in and corrupted. Not at all. That is a created myth, termed by one scholar whose name escapes me at the moment as the "Great Story". The "Great Story" goes that Jesus descended from heaven with his message fully intact, taught his disciples, who then became the sources of authority for the message, who then trained the bishops of Rome, who then held the teaching as pure and true and fought against errors that crept in...
