You seem to adore Marco and have been so thrilled to have him as your officiant. Yes the ceremony is the shortest part of the evening, but it also the most special! Based on your feelings, I think you should 100% stick with Marco @ 6:30.
As for the ending at 10:30 instead of 11pm, I say stick with the attitude nope not happening. My suggestion, throw a fit with the Hilton in an attempt to have them give you a waiver to have music that one night until 11pm. This is after all THEIR fault, and you and Marco both have emails to prove that. And extending their own music cut-off rule for one evening well that is something that is well within the Hilton's ability to do. Forget your current WC, go directly to the director of catering with your emails (andMarcos too if he's up for sharing them with you) and plead your case. That's my 2 cents.
GOOD LUCK!!!!!!!!!