This flight time is really not a good idea. As Jim notes, it is doable but really any glitch that pops up will mess things up. Customs at Miami has become quite leisurely in their processing of passengers leaving the ships, as an example.
Early debarkation is obviously a need for you. It would probably be more helpful if you could do the self-debarkation where you carry all of your bags off the ship with you. This will save some time.