Custody options generally are: Sole (hard to get in many places, have to show a change in circumstances); supervised visitation with no overnights (again if you share custody and the child has overnights you have to show a change in circumstances); and joint with various variations.
It is so frustrating that (1) we know alcoholism is a progressive disease and they almost only get worse, and (2) it is hard to find direct proof of harm to the child (especially a young one) even though you can see the harm. For example, my young child comes home acting out and reflecting all the anger he's experienced and saying "that's a secret and I can't tell you."
For sober parents, giving children stability can a long process that you just document one entry at a time, one day at a time.