It was long but very interesting. I would have my doubts about Nag Hammadi since it is from the tradition of Egypt that Mary is associated with the Holy Spirit.
You said:
It is not unreasonable to suppose that some of these who identified Jesus as "a prophet like Moses" began to think of James, his relative, as "a priest like Aaron."
Since the Messiah is depicted in the Old Testament as a priest and king, it was very confusing for the Jews that there could be one person since the roles of priest and king had always been seperated except for Samuel.