XXB300,
Welcome to SR. There is a lot of wisdom and support here for both you AND your daughter to take advantage of. Please do read the sticky posts at the top of the forum -- several of them deal with abuse (how to identify it, how to safely get away from it) and you can easily print them out and give them to her.
There's a better-than-average chance that he either HAS been physically abusive with her and she doesn't feel it's right to tell you, OR he hasn't yet because she tiptoes around him. Her fear probably controls her behavior, and she knows how far she's "allowed" to go.
I hope she soon realizes that she doesn't have to live like this...that has choices. If you live in the same area, perhaps you could find an Al-Anon meeting to go to together. It may be scary for her, but her actual situation is much scarier. I have known women who are so safety conscious in their life as to be almost immobilized, BUT who still go home to a verbal and physical abuser every night and think nothing of it.
Alcoholism is a progressive disease. It has the potential for getting much, much worse, and often does. You may be able to help in her education, which can only help. But she has to take the next step herself -- establishing boundaries and enforcing them. You can't do that for her.
Hugs,
GL