I agree w/AJ...it's about him and not wanting to go back to the way things were w/him. He's getting a bit stronger, but he's still confused as to why he feels the way he does. His mother is a controller and manipulates him. He's trying to find a way to break away from her. He feels loyal to her because she is his mother and yet, he desperately wants to cut the ties w/her. Again the question will be which way will he go from here.
Your situation is difficult because he is living at home, but my hat's off to you because you've done a great job in dealing w/him. I'm sorry he blew his cork and lashed out at you, but they always say that you hurt the one closest to you. Unfortuantely, he knew he could lash out at you and that you were a "safe" person to do it with.
Hang in there. I do think he's starting to see life a bit differently, but it's going to be a slow process because his timeclock is slow.
Merry Christmas!
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.