I agree with primetime. Parenting doesn't end because he's 18. He needs you more than ever. You have experience to share with him and love to give him. I agree that if he does something illegal, you should call the police, number one because he needs to know there are consequences to his actions and because you want to protect yourself from getting in trouble.
Honestly family counseling would be the best thing for you to help give your kid a chance at a successful life. If you kick him out don't you think he'll get in more trouble. You won't be able to just wash your hands of it because he's not there. I can't imagine how frustrated you must be, but remember if his own mom won't put in the effort who will. You are his last chance because when he's 18 and in the real world, he can really get himself in trouble.

