Just a couple of thoughts - it really takes ALOT for me to keep off the weight. I do 3 days of cycling, 30-40 miles at 75%-96% of my heart rate for the majority of the ride, and 5 hours of high intensity competitive tennis a week - and that's to keep from gaining weight, not losing it. If my max heart rate is 172 with the simple formula of 220-48 (yrs) than I need to be in the 140's-150's and up to be in the right zone, so your rate of 100 or so may not be enough.
Also, it sounds like you're focusing on cardio with the treadmill and riding, and you may want to add some weight training. Even at resting state, muscle supposedly burns more calories at rest than fat.
Good luck!