numbmum,
Sometimes, the hardest love we can give a child is tough love.
Forgive me for saying but he sounds like a self centered brat trapped in a man's body. You know he's playing you n dad and he's obviously played grandparents, he's got dad warped so what else is there?
Let him go. I know it's easier said than done.
Just from reading your post, I feel like you've given him so much already. When does Mum ever cut the cord? When does Mum take care of herself? When does Mum just know that she did everything she could to raise this child?
^^^RIGHT NOW^^^ He's a man now Mum. Let him find out what the real world is like on his own. You don't owe him a damn ounce of your time or energy if he's going to treat you like a piece of sh!t!!! He's going to find out someday that Mum n Dad won't live forever and then what?