Go for the adventure, Jambalaya!
Sounds like two good options, so its about making a choice not about making the 'right' or 'wrong' decision.
Concerning your two questions, addressed in reverse order:
Inside cabin: I've been on two cruises and had a room with a porthole and an inside cabin. I prefer having a window but its not a big deal since not much time is spent in the room. However, the longer the cruise, the more I might want a window.
Cruising independently: although I wasn't traveling on my own on either cruise, I don't see any issues with doing so. Sign up for whatever excursions interest you, spend hours exploring local jewellery stores, and have a wonderful time!
Decemberfire, thank you so much for responding. I totally agree about the longer the cruise, the more you might want a window. I was just too wary of an inside cabin for two weeks - and vacation time was a problem, too. I was wary about traveling alone, but now I've booked it, I can't wait!