Silverado :: Grinding Noise From Tires - Brake Pads Not Releasing

I have a 2005 Silverado Crew Cab 1500 with a 5.3V8, discs in front, drums in rear.

Series of events:

2011- Grinding noise from passenger front tire. Sounded like metal on metal. Removed tire to find that inside brake pad was completely worn down. I thought, at the time, that the pad separated from the plate, and fell off. I noticed at the time that my caliper was stiff (not releasing). No other (apparent) problems at the time. Drivers side pads looked as expected when I replaced them.

December 2012- Grinding noise from Drivers side front tire. I pulled the tire and found that the inside pad was completely worn. All the other pads looked fine. Still noticed that both tires were difficult to spin while in the air.

Feb 2013- Fuel economy has dropped an average of 3 mpg, since December. Started hearing an intermittent squealing/grinding noise from the front end. Seems to only happen when turning left (that could also be from my proximity to the front tire). I had my dad stand outside the truck while driving in circles. He said he couldn't be sure it was coming from the drivers tire. Sometimes the noise is loud. Sometimes its faint. The majority of the time there is no noise. The check engine light came on and I had a C0035 and a C0055. They are a Drivers side front speed sensor and a Vehicle Speed Sensor. Decided to change the drivers side caliper. I used pliers (yes I know I shouldn't have done that) to pinch the brake line to minimize fluid loss. Bled the line.

March 2013- Brakes have partially locked up on me twice in the last three days. I thought there was an electrical fire in my truck based on the smell of the brakes. I couldn't press the pedal. It was like pushing on a boulder. They didnt completely lock, but I could tell they were stuck. The second time it happened I drove immediately home and jacked up the front end. I could barely get the drivers tire to move. I cracked the lines from the master cylinder and some fluid came out. At that point, after reattaching the line, I could spin the tire easier than I have ever been able too in recent history.

Now, Ive read that the speed sensors on my truck are problematic. I'm inclined to think, since cracking the lines on master cylinder released the caliper, that the master cylinder is the problem. I just have difficulty rationalizing that the master cylinder would cause this problem, as of recently, predominately in the drivers side. It could be happening in the passenger tire as well, but it is not apparent.

I also use the parking brake every time I park my truck, even though its an Auto. I don't know why, but its habit.