Sorry; I'm no help with your question, but I certainly empathize with your predicament. I tried applying the BA approach with my husband, but I ran into a different roadblock--it required me to pay way more attention to his drinking/not-drinking than was healthy for either of us. After all, how does one positively reinforce someone's behavior if we don't really know what they are doing?
It sounds like you have an even more intractable problem as there doesn't appear to be much (any?) positive behavior to reinforce. I'm no expert, but that seems to suggest that you need to make some major, difficult, changes if you want things to change rather than trying to get him to change. (And I know, it's so hard, especially with kids). You know as well as I do that there is no point trying to talk to someone who's already been drinking, so why bother with the special dates?
One thing that helped me as I started figuring out what I could do regardless of what he does came from the first part of BA, where it discusses taking care of yourself. Meditation, in particular, helped me to get focused and centered, which then helped me to find a way forward. It also allowed me to deal with his drunken rants without reacting, which deflected and shortened the torment.
Hugs--