My AH always offered to leave - said he didn't need to put up with my bull-crap, that I was crazy, needed help, etc. They always try to deflect any responsibility! My AH always offered to leave cause that was his free ride and perfect excuse to do exactly what he wanted to do - get high.
If it's only your name on the lease, just tell him he needs to go - that he's no longer welcome as long as he's using. He has the best of both worlds right now and you need to change that for him and give yourself some peace. Change the locks and if he comes and starts threatening you, call the police. They will most likely let him get some of his stuff out of the house under their supervision and tell him to leave you alone and give you some options if he comes back.
I wish you the best of luck. I know for me, it took several "practice" runs before I got it right and stuck to my guns and quit worrying about my husband and what he was doing. Give yourself the greatest Christmas gift of all.