Looking for some advice.

When I met my hubby he smoked pot. I knew it and I was fine that he did but I didn't want it in my house and we came to the agreement that he would keep it out (I had a child when we met) and we were fine with that agreement. He didn't bring it in the house and he didn't bring it around the kids. Fast forward 8 years later and we're separated due to him cheating, lying about a stripper and me coming home from work early to find him smoking pot with the baby in the next room playing with toys. 

He admitted that this is a daily occurrence (he was laid off for a short time) and that his parents also smoke around the kids. (I respect that they can do as they please in their home, I wouldn't ever ask them but I did express that them openly smoking when the kids are right there isn't something I'm ok with so they won't go there then) they said I'm unreasonable. 

I feel like I cannot trust him at all. It has been clear that this is how I feel and I feel strongly and he's been doing it around them for so long. And now does it when he's got them. I do not want to keep them from him, I just don't know what to do. Any advice?