If you are not useing the brakes, which is hard to believe, a two ton car has to stop sometime, either you are hard on them or ride the brakes and not realize it or they are dragging (not releasing) or a combination of the above, what kind of mechanic do you have, he should be able to tell you your options. If your calipers are sticking rebuild or replace them, New front rotors and oem pads with everything required like brake sensors, squeal paste etc, If you no where to go it doesn't run much over $100.00, I would not install calipers that just came from a junkyard without rebuilding them first, how is the rest of the system, brake booster, master cylinder, brake lines, replace any of those items if needed, also pay attention to the rear brakes, even though they do not supply the majority of stopping power they do help quite abit, I have seen cars with the rear brakes not working and people had complaints similar to yours. What is not working with your a/c, does it have a leak, is the compressor dead? your car has several possibilities that can cause the system not to operate.