If you can afford, I would do it. My kids are older now, but when they were young and would be asleep before us, it was amazing to take a drink out on the balcony. The balcony isn't huge, but it makes the room so much bigger.
Yes, there are steps/ladders at all the slide points we went to on the carnival excursion. Some did look a little difficult to maneuver. When we went, there was an elderly gentleman that went with his family. With some help from the guides, he was able to maneuver down them all.
Yes, dinner menu is a very full menu with lots of good options at both restaurants. I personally preferred the Chinese options at Chibang vs the Mexican. Dinner is free for one visit to each. A second visit will get $8/per person charged to your account.
The charge for the second visit is fairly new and I believe currently only on the Mardi Gras. You can eat there for free for lunch as often as you want, but only get one free visit for dinner per venue. No reservations, you just select that restaurant in the HUB app when you are requesting a seating time when you are ready for dinner.
The last time we cruised out of Miami, we stayed the night on Ft Lauderdale Beach and then scheduled an uber XL to the port the next morning. Uber XL was 97 plus tip. When researching, SAS transportation was quite popular, but our hotel wasn't eligible.