Hi Jason99, and welcome to Cruise-Chat. I'm sure that you will get lots of great input from the group here. I'll try to answer some of your questions but you'll get many from a lot more seasoned that me.
I know that I could spend 14 days (haven't done it yet) on board as 7 never seems to be long enough for us. Perhaps, if money is somewhat of an issue, you could look at the difference between staying on board for 14 days vs a hotel stay. You could always check out all inclusives in Puerto Rico also. The longest we have stayed in San Juan was two days prior to our last cruise. We have been there several times and there is plenty to do and see there. To answer some of your questions:
1. Some courses are free and others are not. You would have to check in the info provided.
2. Once you have a balcony, you will never go back; it is so great to have it available to watch as you port and just to relax on sea days and no better way to wake up or just before you go to bed that enjoy looking out at the sea.
2a)You can research using the find button in various sections (Port Chat for instance) and get lots of recommendations on beaches and other things of interest that can be done by taking a taxi, public transportation in some cases, or within a short walk that cost very little.
2b) Bringing alcohol on board is a no-no and it will be held until the night before you finish your cruise and its just not worth trying it.
3. FOOD - There are so many choices on ships that I would think that you can definitely get by with being spoiled for 2 weeks. There are great selections in the dining room and other venues on board that come with the price of your cabin. You will find many juice selections, milk, tea and coffee at all your sittings that are included.
I'm sure you'll get lots of help with your questions.