.... the engine would occasionally rev up to 3000 RPM soon after I started driving and was still going 15-20 mph... This sounds like a transmission issue to me, not engine controls, although you do mention the TPS changing the behavior negatively. How did you clean the throttle body and TPS? Check ...

Have you ever drained / flushed the transmission ?

Well if your planning on keeping the car, then it would be worth doing it. And it might solve your problems as well.
Lots of write-ups on it, and a few ways / options on the best procedure. I did the three drain and re-fill's in my case.

Clean out the Idle air control valve

Make sure your throttle linkage isn’t binding