I'm going to ask again about a sponsor, Stands... since you seem so active in Al-Anon, I HIGHLY suggest you get one through your group ... if you do have one, what does she say about all of this, and why isn't she more a part of your life? I've never seen a post from you about it, other than one last year in which you did say you had one, I think.
Remember, you are as addicted as your son. When you feel the urge to get your "fix" (i.e., helping your son), you need to call that sponsor, immediately, for support.
The good news is, each day can be a new start in YOUR recovery. Slips are inevitable. However, you must be able to acknowledge these slips .. and what I am seeing in your last couple of posts is that this part is difficult for you. I don't mean that you should beat yourself up because you made a slip and let him come home for a couple of days, but I'm not even sensing any regret for doing that ... and as painful as it is, regret for our mistakes is sort of part of the recovery process... if that makes sense.
We're all here for you, cheering you on... but also trying to understand how things keep starting over at square 1... ok, well, square 2 maybe?