2002 Trailblazer LS - Under/rough idle during coasting

I own a Trailblazer 02' LS and its at 152,000 miles at this point. I am currently debating on whether its a better strategy to fix this current issue (explained further below) or start saving for another vehicle.

The problem I am having is the truck will sound extremely rough at random periods when im off the gas pedal. Sometimes it will try and shut off but comes back to me when jam on the gas pedal. Also sometimes during all of this, The oil pressure gauge will drop to 0 and go back up once I hit the gas pedal.

Random things: AC buttons 1-4 don't work but 5 does sometimes. It also Idles at 500 RPM's instead of 1000 like I've seen on other newer cars.

Any help/insight is greatly appreciated.

Many things can cause the idle issue, start by cleaning the throttle body, the blower relay up behind the glove box is bad.