Brake pedal does not come right back up after pressing it down

Pedal staying down isn't good, it sounds like it's traveling too far when you step down and it's getting into that part of the bore where the crud has built up.

Hard pull to the left would be a brake issue and is probably causing the first problem, or at least adding to it. Most likely it is a bad hose or caliper on the right side. That brake doesn't apply and the truck pulls hard left. It's also possible that it is a worn steering component but as you didn't say it wanders or is difficult to control I'll stay with the brakes.
Have them checked and repaired and you should be OK.