1997 braking problems

This is my first post to this forum.

I have a 1997 neon with 275,000 Kms on it. It has worked very well up to this point. Recently my brakes were starting to stick. What I mean is when I pushed them more than slightly I could feel that the brakes were not releasing properly and it was in fact slowing the car down. I was able to correct this by stopping and pumping the brakes to the floor several times. A week later I replaced the brake booster because I was getting a sound of gushing air when I pushed the pedal, I thought it would fix the brakes sticking too. The day after replacing the booster, my brakes with only 5 kms driven would not release at all. My mechanic released pressure on the brake line and I drove the car to the garage. He replaced the right flex hose and caliper and it seemed fine. Later the same day same problem again...brakes staying on constantly (both sides) after a short period of driving and braking. I still want to fix my car. Anyone have any ideas?

Just a note,
My ABS brakes have not worked in 2 years(light on). Since the booster was replaced the engine light and battery light is on as well.

As a follow-up, I read the engine codes today from a list I found here and I am getting code:
12-Direct battery input to PCM was disconnected within the last 50 key-on cycles.
44-Battery temp sensor volts out of range.

Any help would be appreciated.

the cylender in the caliper that clamps the pads on the rotors might have gotten gunked up and isn't letting them return into the caliper once you let off the brake, so take a look at that and maybe get some new calipers