I have a ball python like this he is highly defensive and I have had him for 6 months, I usually let him engage in his "Im going to bite you now stance" and I tap him in the head with the snake hook (not hard but enough to break his concentration) then I take him out and he usually balls up. When he does that I cup him i my hands to dominate him so to speak. I think alot of the problem with the snake and yourself is acclimation to one another, he was use to a certain thing with he previous owner, So my advice would be, to be consistent with what time you approach and become methodical about how you handle him until trust is gained on both parts. Then hopefully you can enjoy him fully.