if you have to leave him,
be careful of trying to get back at him through any means of divorce or with custody battles and children. I know all to well how it feels to deceived, My first poly relationship I wasn't even aware of it.
It's hard to not be pissed off and hurt when you look back and realize all the shitty treatment and making you feel like an asshole was really them lashing out due to guilt. I am sorry you are experiencing this.
It took years to get over the anger and resentment, but it does happen, although I still don't contact one of the women who put me through that. Co-parenting after a divorce can happen and doesn't have to get ugly, but it was hard to always remember that, and I am so glad I never made it any worse than the divorce already was, but it does eventually get better, and you can still work it out with husbands however some people aren't capable of being 100% honest, but I know that is what would have made a difference in my relationships, even after the fact and all the hurt.
But they weren't willing to do so, and because of that, I am seriously glad that I didn't stay with them
hang in there