I am sorry that's read you are going through so much. It sounds like you really do need to evict him. He is an adult he should be supporting himself. You might want to call your local domestic violence hotline. They may have support services for you.
In the meantime. Your son could be considered a tenant even without paying rent. If I were you I would write him an eviction notice and mail it to him registered mail, return receipt requested. That will get the ball rolling to get him out.