This is not a long over detailed rant! I am so sorry you are going through this. I myself am going through a similar situation. You are definitely doing the right thing by keeping him AWAY from your girls.
Remember this: YOU DID NOT TURN HIM TO DRUGS. IT IS NOT YOUR FAULT.
He is doing this to himself. You didn't have a say in any of it. Anyone can go and use drugs if they wanted to but we CHOOSE not to. He has that choice just like the rest of us. Don't let him convince you that it's your fault even in the least bit or that what YOU do can help him get clean. This is my most recent realization. HE has to do it for HIMSELF by HIMSELF.
Hang in there love. hugs!!
xo