Simply, my suggestion is to go to an al-anon meeting, RIGHT AWAY!!! Please share. Just because he's going to treatment doesn't mean he has to move out, none of that makes sense to me, but at the same time, was your relationship unhealthy?
Addiction affects everyone, and on your side, I think mom needs to butt out. I agree he needs this time to take care of himself, but guess what???? You need support too.
Please go to a meeting. :ghug3