hey a few words of advice here.
When growing up my brother and I had VW beetles to drive to school. So we learned that when you buy a rig first thing to go through is the brakes. Why? Because you are driving a missle that can cause serious injury or death. I see that you are working on your brakes good. we found it easiest to just replace the whole system since Vw's are known for having issues once the master cylinder has been run dry, these rigs sure felt like it. So the systems worked flawlessly.
sounds to me like you need to think about bleeding the lines. I just had one very similar and here is about how it went.
My soon to be mother-in-law's s10 was having issues.
Several months ago she had brake pads replaced front and rear with carquest el cheapo's and someone had topped off her fluid for her.
She now complained that the rig was weak and barely made it the 1 hour drive to town.
She asked me to replace the fuel filter, did that in a snap, and the fuel economy got better but the cel would still come on up long steep hills.
Most of that a gravel road in the summer and a mix of ice, snow and gravel in the winter.
I replaced the pads, free'd the siezed float pins greased appropriate items with caliper grease and replaced the rotors...since the rotors were hosed big time.
Then drove it around my block and the brakes were locking up. When it cooled down it was fine but when it got warm the brakes would lock up.
Well turned out that the rear passenger side had been a problem many times in the past so in bleeding the brakes I had to remove the bleeder on the pass rear and clear it of sediment, even though it had a cap on it.
Bled a bunch of air out of that side and flushed the whole system when I found out that someone had added powersteering fluid when they topped off the fluid for her a few months back.
I had to ask some q's because the fluid was dark green and smelled burned.
So your wondering why the comparison with the s10, small light rigs with about the same systems. brakes are simple, however at times they require 2 people to work on them.
Good luck on finding your problem and remember dot 3 only in the brake fluid as well as it should be clear and other color it needs to be changed out.