That sounds like a similar situation to me a couple of years ago. They really do have to realise how bad it is themselves and decide to speak to someone about it. My partner went to the GP for various things but I had to speak for him then he’d stop me anyway, also he went to one cbt session then refused to go back. it’s so frustrating and until it came to a head a year later when I felt it was the end of the line for us (not as blackmail towards him but I actually felt it and he knew that) I would have left but he seemed to decide a couple of months later to get help.
You can only keep trying to talk to him gently and encouraging him to do something about it. Hopefully he’ll realise for himself soon that he needs support.
You mentioned cheating, that’s something I have put up with in the past from other partners and I couldn’t deal with that again.
It’s all a balance in deciding which life is more detrimental for your children.