Can you run?
Now don't take that the wrong way, obviously anyone can run with the right motivation (hungry tiger nipping at their heels for example), but are you able to run for fitness? Some can, some can't, some simply wont. Different strokes.
But I gotta say, I am finding the best success (2-4 pounds a week consistently) since I started running 25-30km a week. I used to hate the very idea of running and thought joggers were morons. However, based on soooooo many of the success stories here and other places, running seems to be far to valuable a tool to ignore. Since you are already closer to your goals than most, your body may be able to handle running easier than others. So far all the biggest success stories I have heard of incorporate running more often than not.
Now running is my primary exercise. I used to do tae bo 3X week, weight training 3X week, yoga and pilates and core exercises thrown in for good measure. I was working out 2-3 hours a day, 7 days a week. Whereas I felt good and was getting fitter, I wasn't losing weight as fast as I had hoped. However now I have pretty much stopped all of the above exercises in exchange for running 5-10km 5-6 times a week and have hit a weight lower than I have been in 25 years! I really believe running is making the difference.
Now like I said, running isnt for everyone. But after seeing how much you are struggling maybe it is worth a shot. Since you aren't obese your knees won't be at risk like bigger folk and it may just kick start things for you. I know for me running has changed my life, literally. I feel like a giant a$$ for not taking advantage of this exercise years ago.
Might be worth a shot.
sirant