I don't know about child custody and visitation when a baby is born to parents who aren't married. But I would be extremely concerned about my children staying with an alcoholic. Even if it's a "weekend alcholoic." And I do think you are right. From what you've described, I don't think he wants to be more than just a part-time dad.

Was he a good father to his bio kids?

There is no arriving, ever. It is all a continual becoming.