bren,
My heart hurts for you, I know how this tears at you and eats you up.
It seems as if your son is just not at his bottom now, and if you rescue him, and let him come home, it will just prolong his journey. (At least that's my honest opinion..)
I have been where you are, even dropped my son off at the homeless shelter, it sure wasn't pretty, let me tell you. Unfortunately, you know, and I know, they have to do this for themselves. Turn it over to your H.P. and let him lead your son.
Hugs,