I can completely relate to how you feel about OW. In my case, my H did have (and maybe still does) have an EA, and I know that they kissed. H and OW work together very closely, they sit next to each other and are in constant communication.
I'm not in R, but my H has said a few times that "there's nothing there". However, he still wants to be "friends" with her, defends their "friendship", tells me I have no right to tell him who he can be friends with, and thinks I'm crazy about getting upset over OW. And he also doesn't think that he cheated. I know I'm a long ways away from R with that kind of mindset.
I wanted to say that I think it's ok to not want J talking to OW or hanging out with her. He broke your trust and it needs to be rebuilt. The problem is that it takes a long time to build that trust again and J needs to be fully cooperative and transparent in his activities. You can start by making a decision to trust, but the actual building of it is a long process. So don't expect to trust him again overnight.
I get that he's young and doesn't want to give up his social life. And he shouldn't have to give up his social life completely, but he does need to rearrange his priorities. He has a family now and he needs to put you and the kids first. Sure, he can go out for a drink or two, but the frequency and length of his outings could perhaps decrease a bit.
