Do what we did last week. Hire a car with the driver. We had 3 days in Bali and on one of those days we had the tour planned. It was amazing. I'm hooked on Bali now
The tour for 2 people was $60 for entire day (everything included besides tickets to temples, which were cheap anyway). Not hiking and not snorkeling
Why would you do hotel hoping for food? There is so many restaurants around. Just search the area on google maps around your hotel and you will see what you have there.
Airport - Just ignore hundreds of taxi drivers at the arrival area of the airport. That's the only negative thing about Bali. Arrange your car before hand.
As for departure, You can't be there more than 3 hours ahead of time. They open the ticket counters only before the flight. Then security bag screen, immigration (fast track for you) and security search. All that didn't take more than 20 minutes (also using fast track).
The lounge situation is so so. Forgot the name of the lounge but there are 2 right next to another. Priority Pass lounge and the lounge which most of the airlines uses(we used this one). There is no air con in the lounge. They have couple of portable wind blowers.
We just had cold beverages, as the food options (looked good) had few 'visitors' walking between the plates. Spend few minutes in the lounge and decide for yourself if you want to stay there. Next time I will go to the restaurants downstairs by the gate area.
Enjoy Bali