Interesting story. I know what I would do, but what makes the world interesting is everyone is different. :) I, personally, would figure he made a decision, a thought out choice w respect to any of his consideration toward you. It was his right, his choice and he owns it. Likewise, if he wanted to see me and I felt up to it, I would make the "meeting" on my terms, or nothing - that is your
right and your choice. If I felt the wedding wouldn't qualify as "on my terms", then I wouldn't waste 3 seconds checking "no" on the rsvp, advise him to get a refund on the ticket, have zero regret over it, send a nice gift, and be done w it. I think it is pretty inconsiderate of a grown man to expect you to go under the circumstances in the first place.
However, I would also forgive him. For your own sake - not his.