To me it looks like he is showing you who is the dominant one being HIM, he did not want to be removed and he is letting you know by biting, the only thing I can say is and don't bite my head off because I know he bites hard do not pull your hand back like that when he goes to bite you he has learned that when he does that you will pull away and not make him do it, I suspect thats why he does it, it all boils down to behavior he is learning he can get his own way by biting and its becoming a nasty habit now, I bite and she won't remove me I would get out a perch and when you want to remove him use it so that he knows when you say its time to come off it happens and hopefully once he realizes that you will follow through you can re introduce your hands. Don't know if its going to be helpful for you but those are just my opinions 
