1. Renting a car and paying to park are going to wipe out any of your savings from the grocery store. Just grab an Uber or Lyft for like $5 and go to the store. Do you have a lot of side trips planned that you need a car? Yes, hubs and son are golfing and bringing 2 golf bags. Not really doing groceries for savings, to eat in room while getting ready rather than having to stop for breakfast.
The dining plan would be overkill and pricey for us. I can share a meal with my youngest. It's not like you want to lug around leftovers so underordering is sensible to avoid food waste. My guys are big eaters but I'm not and shared meals with my d the last time I went. Seemed like, even with sharing, we'd be spending close to $20/meal. I'm thinking $60/day/person for Universal dining doesn't sound too bad. It includes express meal ($50) and sit-down meal ($120) with a snack and a drink ($20)...so a wash and assuming I'm underestimating for 3 adults?
2. The less I have to carry, the happier I am. Free cups of water work for me. The camelback will have to go in most lockers so no use while waiting in line. But, it's not a bad idea. Better than bottles, imo as hands free.
3. Someone can hook you up with that info. I'm not sure it's always open.
4. I can't visualize your scenario.