On your point about early Christians and the son of God, Larry Hurtado shows a "high christology" right from the start.
https://www.google.co.uk/amp/s/larryhurtado.wordpress.com/2013/12/18/early-high-christology-clarifying-key-issues-and-positions/amp/
He has alot of essays available on his personal site so don't necessarily have to buy his books. He also has interesting work showing from a historical perspective, the best explanation for these developments in religious practices are religious experiences of the practicioners. In other words , revelation from the holy spirit shows Jesus followers that he is now exalted at the father's right hand.
So all Larry's work just backs up the scriptural picture. So instead of reading Larry just read the scriptures. But nice that someone has put in rigourous historical work without first taking up a doctrinal position and reading back into it.