I’m sure you’ve considers all options so I’m sorry if you’ve thought of this, and for some reason dismissed it.

But can’t you demand child support. Really demand it. With lawyers.

It doesn’t cost all that much. And then suggest you will drop the support demands if he signs a name change.

Selfish people are selfish to a fault. He may see it as a means to spend more on his addiction. And give you an out.

He is never going to pay child support anyway. You’ve lost nothing and gained your maiden name for your daughter.

Just a thought.

Another thought:-

I’m sorry this is your reality.