Yep, he's rebelling and the comment about "not owning him" is very telling because he's looking at you as an authority figure. Continue to ignore his behavior and no more talks about the marriage or separation/divorce. I'm glad you wished hin a good trip.
Enjoy your time in Dublin. You need a break and this is the perfect place to have a bit of relaxing time. I love Dublin! The people of Ireland are wonderful and very friendly. It's amazing how much the landscape changes from one city/town to the next. Lots to see and do.
Now, about the wedding/weekend away. It's up to you, but I would still go. It's a great opportunity to visit w/family and also to show him how much you sparkle and can have a good time regardless of his behavior. Nothing says you have to stick to him like glue. Again, it's a great opportunity to visit w/family.
I do hope you have a good week. Don't worry about your h, when he sees that his behavior isn't affecting you, he'll settle down and be civil again.
Sit quietly, the answers will reveal themselves when you least expect them to. The past is gone, the present is a gift and you need to focus on today, allow the future to reveal itself when it is ready.
