the reason that your torque plate won't come off the caliper is most likely that the boot on the thing is torn and it's rusted and stuck. some PB penetrating lube is useful, but the most reliable way is the crowbar trick, pioneered by me:
1. get a friend, a large crowbar, and a benchvise attached firmly to a heavy-ass bench. alternatively, have a third, very large friend stand on the torque plate.
2. insert the crowbar between the torque plate and caliper very close to the place where they are attached.
3. you + friend lean all your weight on the crowbar and pry that beotch apart. be careful because it may fly off. the landing on your face isn't so bad, but the landing of the caliper on your head hurts like hell.
4. drink beer and rebuild the caliper (or just replace the damn thing)
of course, there could be something else wrong with it, but if it was stiff at all, then this is most likely the reason. good luck.
btw: 500th post. i rule