Ok you are going about this from the wrong end. You need to separate while he sorts himself out. For his sake. (And yours obviously).
Then he needs to decide if he wants to get sober for him. Not for his DD and not for you. He also needs to decide for himself if he is going to get help or not.
Meantime you need to decide if it's worth waiting the year or more this will take.
Then when he has sorted his shit he needs to win you back. Start again.
You really ought to tell you DSDs mum too. But I'm sure she knows. At least tell her you are leaving.
For the record my ex is like your H. He still is. Our kids no longer see him - their choice aged 8 & 9, to go to court to stop it.
He still hasn't admitted that the problem is his. He destroys everything in his life. None of his family see him. Not one person. He cannot maintain friendships because guests are a legitimate excuse to drink and he is an evil drunk.
I used to think he was ill - but having read "why does he do that" by Lundy I came to the conclusion that actually he is just a c**t.
Good luck OP. This is pretty much the low point. But make that decision now for everyone's sake.