I understand your compassion. For me, I never treated my xabf cruelly, and I get to live with that -- hold my head up high and be proud of treating another human being with dignity.
As possibly in your case as well, mine never put up a fight. When I asked him to leave, he did so as soon as he could manage it. Even though he was not on a very healthy path, he had his pride too.
I don't know about the legal ramifications should he choose to stay - I would suggest talking to the landlord or law enforcement, or perhaps there is a tenant advocate in your area -- you could google that. But I do know enough about landlord-tenant law to agree with noday -- you still do have a lease in force.
Best to you. This is extraordinarily painful. But you are doing the right thing.