Hang in there - I second everyone, you did nothing to cause his drinking.
I, too, felt like "I made a mistake" few too many times and I had to pull out "reasons I am divorcing him" list
You are responding to behaviour - anyone whose children are endangered by an alcoholic is bound to be very frustrated.
My XAH was doing ok for a while - and when he was visiting with DS in my house (where we used to live together), the sh@t hit the fan - he went from complaining about his current living conditions at his brothers (very cluttered, large dogs, not too clean), to urging me to see my role in deterioration of our marriage, calling me a B word...all his old behaviour. Thank goodness my son did not hear it. Threatened to leave a few times which would upset DS - I told him to do what he feels is right, and he never left. So basically he was pitching a big ole fit and I refused to react. I did tell him that if he is going to use foul language, he has to leave. No sir.
I am asking him to have supervised visits elsewhere going forward. It is taking me a few days to recover......