Please let go. He is just manipulating you big time. He is refusing to get help from any other resource...because he does not want to get clean and sober. If us addicts are really serious about getting clean and sober...we become willing to do WHATEVER IT TAKES to get us there. He is not serious about getting clean in any way. I can promise you that.
He knows all he has to do is sweet talk you and he's got you jumping through hoops with "hope" and "fear" as your major motivators.
Let him go to Mom, or the streets. But let him go. If you take him back you are helping to keep him an addict. If you really love him put up that wall of protection around you, and refuse to budge.
I know it is hard. (And by the way...I'm speaking from HIS side of the fence.)