A half-way house is a good place for a recovering addict to be. I do know exactely how you feel. My AS is 42 & because of my parents enabling his addiction has gone on for 20yrs. If you take him back in, it could wind up ending the same way it did last time. This is something he has to do for himself. It takes alot of love to say no. It is harder than saying yes. If you said yes you would feel better BUT is it the best thing for your son? I don't think so.
Trust your sons HP to take care of him.