I hope X's life does not become hellish. It would not make your life better, it would not be good for the kids.
Will his R with his GF work out? Maybe. But I'd guess not -- it is weird for him not to take her to the wedding. Either way, there will be some emotional stuggles to work through with respect to that R. This is true of any romantic R. And, most romantic Rs fail. A painful truth, but not one that makes a person's life hell.
Will he confront his behavior at some point and start to feel some guilt about some of his choices? Probably. This does not mean that he will seriously question his choice to leave the marriage, nor that he will conclude he should have remained married. We all have regrets. We live with them and can have happy lives.
Focusing on his projected future unhappiness as a way to cope remains seriously co-dependent. Don't let your friends, family, or the boards drag you down that road. Your emotional welfare should be independent.
Try to quit cataloging and analyzing X's choices and actions. When you start doing so, put a big "DON'T INTRUDE" in your head, for his life is not your business.
Resist any urge to revisit the Father's Day shopping question.
What are YOUR plans for the weekend? Maybe you and a friend could drive out to the vineyards to some wine tastings? Go take pictures of your favorite color in the city?
