Two problems:
1. I still cannot achieve a firm brake pedal even though I have bled the brakes multiple times, both with a power bleeder and the old-fashioned method of pumping the pedal.
2. My rear pads have worn down to nothing and my front pads look new.


Here's the short version of my brake problem history:

I've had a soft brake pedal since I bought the car almost four years ago. The brakes seemed to work fine though, as well as the ABS - I had to make an emergency stop coming down a hill a few years back and the brakes performed perfectly.

In the past year or two I have noticed that my rear wheels lock up (engage ABS) before the fronts. I attributed this first to the rear calipers locking, then to the ceramic pads I put on the rear being too aggressive.

I have replaced: the master cylinder (expensive); the front calipers (expensive); the rear calipers; front and rear rotors (ATE); front and rear pads (AXXIS Semi-metallic); brake hoses (Meyle); and I have bled the brakes about a dozen times, using around two gallons of DOT 4 fluid (expensive).

What else could be wrong, and how can I get a firm brake pedal?

I'm about to the point of taking the car to a shop and saying "Do what it takes to fix it." And I HATE doing that.