Wow.. late to the game.. sorry.
You made the right choice. Money can be re-made - but hellish experiences is wasting more than just the money. Definitely bag out of the trip. If it's airlines, you can let them know "something came up and i need to cancel or reschedule the trip" and some will give you a voucher with a time-limit to when you can reschedule the trip "for a reactivation fee" which is better than paying full a 2nd time. See if this is possible for each leg of the trip (plane, cruise, hotels, etc.)
yeah.. your bf is not over the ex- and that he'd flaunt it is not a good sign. That he blow you off to spendnn time with the ex-, then blow you off again after just being with ex- - not good news. he's losing out. you can do better.
Good luck to you.