"I don't feel comfortable going on this trip." "I won't go on the trip UNLESS you cut contact with OW." "I won't go on the trip BECAUSE you won't cut contact with OW."
Listen to your gut. You either feel comfortable or you don't. He's right - you either trust him or you don't. If you know you can't trust him, then you know you won't be comfortable. That's your boundary. The other stuff is control. He's done nothing to earn your trust, and if he capitulates because of your conditions or reactions, it will not be genuine. You might get what you want by controlling him, but you won't feel safe in your gut. The gut always knows!
Look at his weasel words. "I need to be completely out of contact FOR THIS TRIP with her." His weakness is both pathetic and staggering. There's only one answer that will satisfy you, I think, and he's not giving it. "I have permanently deleted and blocked all possible forms of contact with OW." He's just flattering you to buy himself more time while he gets the prize of the family vacation. "It's for the children!" Using your children to guilt you is awful and manipulative.
You will not enjoy being the marriage police and he will resent you for it.
