It sounds like your primary problems are gearing and fit. Gearing can be changed easily, but fit cannot. If the bike is not a good fit, then I don't think I'd put a lot of money into it. I will say that Trek claims the FX weighs about 27 pounds -- that's not all that heavy. I think you'll be hard-pressed to find something that's appreciably lighter. You might ask your local bike shop to weigh other bikes in the same class to see if you'll achieve a significant weight savings by switching to another bike. If you do decide to sell it or trade it, I'd advise something with a carbon fork. That's going to be your best chance of finding a package that's noticeably lighter.

Best of luck!