Thanks everybody. I have an appointment on Tuesday with a lawyer from the top family law firm in the city (earliest app't I could get). It won't be cheap or easy, but it will happen.
I've been logging everything since ex really started going off the rails in February 2016. I have a single-spaced 35-page document detailing event by event, date by date, which could easily be turned into an affidavit.
I have requested the police report of the incident, followed up with child protective services, and have spoken to staff, parents and observers who would be willing to give statements.
I received a plan of action from ex in which he says he'll go to counselling, start going to AA, carry a breathalyzer, etc etc. But the same message also contains a long-winded justification as to why this is all his second ex-wife's fault (because the divorce is stressing him! And he can't sell the house!), and the words "I'm sorry" or "I take responsibility" are conspicuously lacking.
I did not respond to his message.
I have to keep reminding myself that there are some things that you don't get do-overs or second chances. I think about domestic violence - what I would do if a friend told me that their spouse broke their arm and asked whether they should give the spouse a second chance, because maybe it will just be bruises next time. I would say "hell no, violence is zero-tolerance, second chances are not one of the options". Endangering a child through drinking is like that too, even though he didn't deliberately intend to risk her life (and don't abusers say that too - "I didn't mean to hurt him/her, it wasn't my intent, it just happened"?).
I know I may be my own worst enemy here. I need to keep reminding myself that yes, it really is that bad, and yes, I am being absolutely reasonable and responsible in restricting his access to her. Giving up on the hope that she could have something like a normal relationship with her father despite his addiction is going to be hard.
And a big no to puppy-blackmail.