Sadandtired you are not responsible for your (not so D)P, and the ?family? that he treats so badly breaking up will not kill him, trust me, his behaviour is learnt and all about making you feel for him instead of for your child.
As you say What he wants always comes first, any sign that isn?t happening and he uses a range of behaviours to enforce it and you?ve been ground down into accepting them.
You are responsible for her, and I?m sorry but right now you are allowing long term damage to quietly take place. He has successfully (intentionally or not) groomed you to believe that leaving his abusive behaviour is bad and wrong, and your responsibility is to him, and no one else, and that?s the lesson she?s learning too.
Breaking up with him won?t have a terrible effect on DD, it may bring short term unhappiness, because change is stressful, but staying with a man who treats her and her mum like this, while mum backs up the idea that it?s normal and the important thing is to put his wants first, live round his volatile moods and violence, now that will have a terrible effect on her.
Look at your little girl and imagine her in a relationship with someone treating her like this, what would you be saying to her?
We make mistakes, the trick is to forgive ourselves, sort them out and teach our DC?s better skills.
Call WA now. If you can?t do it for you, do it for her.