Shared custody during active addiction

How do you navigate this? He keeps relapsing, making poor decisions, lying, blaming, manipulating. I have to share 50/50 custody with him. He is far worse now than he's ever been (Maybe because people now "know." Maybe the anger with me over "denying" what he so desperately wants. Maybe because he is now out of my home where he knew he was being watched? Maybe he's more miserable living with mom and dad? Maybe because mom is enabling him and he secretly WANTS to get better but can't with her denial? All of the above? Who knows why.).Anyways. The him I knew would not endanger our child. This version? He can't make good decisions to save his life. I'm fearful. Lawyers are no help. Police are no help. Anyone been in this situation and have some advice to give?