The very root cause of your unevenly worn pads are the SLIDE PINS. 99% of the time this is the cause. Unless you are dealing with a two-piston calipers such as on front brakes. There are some pretty laughable answers in this thread, but bottom line is 1) You need new pads now AND you need to clean and re-lube the slide pins or you can replace the slide pins and boots. When the slide pins are sticking, they move at different rates relative to each other and this causes one side of the pad to rub harder on the rotor than the other side. I don't understand why you pushed the piston down if all you planned to do is flip the pads around. That was just throwing gasoline on your fire as it gave you additional problems. Don't just throw a new set of pads in and call it a day. You haven't fixed the problem if that is all you do. With new pads and good brake greased slide pins and the caliper re-installed on the vehicle you will find that the brake pedal will go to the floor on the first 2-4 pumps then it will stiffen and rise to its correct height. After that, bleed the brakes properly and carefully take it for a test drive.
