And if it doesn't end with them, then it ends when WE say "enough".
I'm sorry it continues, Louise, and I hope this is the jolt he needs to get back on a good path.
I'd do the same thing you are doing, at least as long as his actions show a genuine willingness to get clean and stay clean. For me, the hard part was asking my son to leave if he couldn't respect my boundaries. It got easier when I realized that, at that point, it was serving no useful purpose for either one of us to allow him to stay.
He may be struggling, but I see your recovery shining through brightly.
Hugs