Not without a fight

I said that. I said that I would not lose her again, not without a fight.

But how do I go about that fight? She isn't a prize to be won. She's not a trophy to put on the mantle for show and brag about.

She's a person with thoughts and feelings who really does deserve better than what she has.

Months ago, I had the opportunity, with a few well chosen words, to get her to leave DH. But that reason would have been "for me". That was the wrong reason. She had said that she was going to leave for me.
While I believe that I am a better option, she needs to leave for herself, for her reasons; because she's not happy. (and I don't think that he will be able to make her happy). I told her that.

I have tried to stay as "noble" as possible and keep only to the facts. I have pointed out his shortcomings and the things he has done to get us to where we are today, but that just seems "wrong". Like I am in some mudslinging campaign that politicians do.
But what else can I do?

The big concern I have is the threats he makes. It has proven to work. She says she wants to leave, now he knows all he needs to do is threaten to take the kid, or kill himself, or tell her parents. He knows she'll fold. That button is there now and all he has to do is push it to get what he wants. Who knows what other threats he's made.

How do I fight that? I'm not him. I even try to not give her any direct advice. I put my thoughts and feelings here because that's what this is for.

How do I fight a fight that I am restricted in? I really believe I am better than he is, but how do I keep it up without stooping to a low? How do I do this?
I have always been a man of action and the lack of it is driving me nuts.

I will not lose her, not without a fight, not again. But how? I got some thinking to do