There's only "no winning" as long as you keep playing the game.
You can decide to stop any time. That is the ONLY way YOU win.
It's pretty clear to me he's not ready to quit drinking. It's pretty clear to everyone else, too--the therapist, the rehab, his employer, his parents. You may think of yourself as some kind of hero for "believing in him," but there's nothing heroic about believing in a fantasy.
In between interceding with his therapist, the rehab, being at his beck and call when he decides he doesn't "need" rehab, what have you been doing for YOURSELF? Why not invest your effort into something that will give you a good return on your time, energy, and emotions?