What I did was not drink at home. If I was out and had a drink that was fine. I simply didn't want to have any booze in the house.
It didn't 't make any difference and I ended up leaving 2 years ago but it seemed like a good idea.
IMO, don't let him put the success or failure of his program on you. You can't make him drink and you can't keep him from drinking.
Your friend,