Givenup….you have gotten some good responses, I think....I really liked what SparkleKitty said.....
I will add this....alcoholics who are actively drinking, frequently follow the pattern that you describe....seeming to forget what happened, the night before....that is because they really DO NOT remember it. It is a form of alcoholic "black out". they may look normal to you the night before, but their short term memory fails to become "registered" into their long term memory. Sire, you remember all of if, but to them...it never even happened.....
You may need to change your expectation that he will remember what he says or does when he is drinking.....
It becomes easier to detach if you are willing to give up a lot of your expectations....yes, and give yo the need to be "right".
Detaching from an alcoholic is hard....because the playing field is sooo not level, to begin with......