It sounds like you're definitely going with the right attitude for freestyle! I'm fairly new to cruising, with only 5 completed cruises -- all on NCL -- and part of the reason we didn't start until recently is because I hated the idea of assigned tablemates. I was afraid of ending up with someone like you described. The nicest thing about freestyle for us is that you can either choose to dine alone, or with others if you meet people with common interests on the ship. We tend to meet "friends" from a roll-call group from another board, and seldom eat with the same people twice on a cruise.
As far as excursions, I don't do small planes, so that eliminated the most costly excursions for us. In Juneau we went whale watching with Harv & Marv, one of the independent vendors. In Ketchikcan we did the cruise to Misty Fjords (through NCL), and in Skagway we did the longest train ride where you go by bus one way to Carcross and clear back on the train the other way. As early as you'll be there, I doubt that one would be going yet. Our cruise on the Pearl was our 2nd to Alaska, and we've also done a Mendenhall Glacier/City tour in Juneau, a tour to both Saxman Village and Totem Bight with Sourdough Tours in Ketchikan, and rented a car and drivent to Emerald Lake in Skagway.