Here's my take on the encounter with your X and the ow.
XH gets caught up talking to you. I mean you two have a history and children in common, and you are at the concert of one of your blessings.
XH sounds like he's enjoying the conversation and then remembers, oh no, ow is sitting over on my other side probably getting more and more pissed while he's virtually ignored her, and he's talking to you about things she is not a part of. He kisses her, not to make you jealous, but to placate her because he knows if he doesn't do something he's really going to be in for a rough time when they get home.
ow's are a very insecure lot. They have a lot to compete against. Not only history and children, but memories too. I think once the MLCer settles in to their new life and everything that was once new loses its luster, they can't help but look back to what they threw away.
Your XH sounds like he has a ways to go, but being able to have a friendly R with you sounds like he is definitely progressing through the tunnel.
I agree, get back to being detached. Then you'll be able to sit back and watch the show without taking anything personally, as I truly don't think he kissed her a couple times to make you jealous, but to try and save himself from what was going to come later...
I will tell you why I view it this way. Last spring when D13 took a vacation with H and ow, D and H were talking about family history. D was facing H and ow was sitting apart and behind H. D said that she could see ow getting more and more upset. The ow was eye rolling and her face showed her anger while the conversation was going on. D said that she heard angry words exchanged between ow and H later on. D didn't know what was being said, but I figured it probably had something to do with the earlier conversation between D and H.
Get some more popcorn and keep living your best life!