Sounds like you clearly established a boundary for yourself and made it stick. I see no problem with what you've decided and think you're handling it beautifully. It also sounds as if your AH is trying to test that boundary with all he's got and is somewhat dumbfounded about your steadfastness. He's starting to quack (i.e. "we need to do something") and flap his little wings uselessly to try to get you to comply (where's the smiley that represents that?!).
I don't think you're controlling his behavior in this respect. The fact that he needs YOUR car to go out drinking seems rather infantile, like "Mom! I need the car!". If he wants to go out and get blitzed, then he can find his own mode of transportation to go do it. You've just decided not to make it EASY for him to go out.
Nice.