I, on the other hand, don't want to sell the house and then split the proceeds with him so that we can drain the money dry all while I sit anchored to an alcoholic who is quite capable of running our financial lives into the ground if he gets another DUI or similar problem.
That sounds like a sober mind speaking, there. And I think you handled that beautifully -- not arguing, not telling him "you're nuts" (although you thought it) -- just saying "I'll think about it" and then leave it at that.