He does not sound like someone to be trusted with the child. Speak with the family law attorney to see if it is possible to write drug and alcohol monitoring into the parenting plan. You should have a good case, given his run-ins with the law
You could always ask for random drug/alcohol screening without court, especially if you suspect prescription drugs in addition to alcohol - he may refuse but trying won't hurt I don't think
I hear Sobelink is good. I finally started to let DS have overnights with dad - but dad stays at his mothers so there is a "built in" supervision there. And he is doing tests randomly - has been for a year now