I would be very surprised if you did separate the alcoholic from the father. It is the same man, regardless. And if he really took care of her as a father should, he'd be more respectful to you, her mother. And he'd get his own stuff together in his life.
I agree with the others...you did a good job by setting a boundary and acting on it. Yeah, it hurt you in the immediate moment, but it will pay off in the long run.
Can you find others in your life that are kinder and more reliable?