The formal night will be in Nassau. There is no other time to do it given the realities of luggage transfer on the first and last nights. Trust me, on a 3-night cruise formal night is not a big deal.
RCI doesn't allow any personal alcohol brought aboard for consumption, including wine.
There is a charge for the sushi bar on the Monarch Of The Seas. I forget how much it is.
Royal Caribbean is comparable to Carnival in most respects, and this is especially true when comparing older ships such as the Monarch to a Fantasy-class ship of Carnival.