You are wise to hold firm to your boundaries and keep a safe distance for now. Also, you are wise to have kept your child uninvolved right now, if these situations throw us off balance, you can imagine what it does to a child.
His life didn't end with his arrest. He has something he must deal with, that's just life on life's terms. He can still continue a good path and stay clean, or he can use this as an excuse to give up and give in.
Funny how it can be with addicts, they may stay clean on their worst day and use on their best day, or vise versa. Thing is, they use or don't use regardless of anything we do or don't do.
I hope that this arrest is exactly what he needs to address cleaning up his past and preparing for new beginnings when it is over.
Hugs