What is wrong with my car?

I've got a 2001 Dodge Durango SLT 4.7L V8, 4x2, automatic transmission. Several months back I had a problem where the engine would overheat, water was not properly flowing throughout the radiator system. Only the top hose was hot, the bottom was cold. This seemed to go away after replacing the water pump, thermostat, and bleeding the system for air pockets. Yesterday, I put more water in the reservoir and I opened the radiator hose, saw there was no water in there, and filled it. It also had issues with the crankshaft position sensor, the original burned out, I replaced it, then the replacement burned out, and I replaced that one with a Mopar OEM part.

Now today, I'm getting the same symptoms from the car that tells me the fourth CPS is going bad: overdrive coming on and off, RPM surging, stuttering and jerky driving. I shut it off for a while, started it up again, seemed to be mostly doing okay and then I started getting the overheating problem again. I don't know if maybe they're related somehow? Also, the first CPS went bad before I started getting the overheating problem.

I can think of a few explanations for the CPS: the connecting wire for the CPS is bad, or there's some other short in the system. I don't have a volt meter to test things out with.

For overheating: more air pockets in the system, or another failed thermostat. Or, the used AC compressor I installed (it has a loose front end where the belt loops around, it squeaks a little bit) is damaging the belt.