Seems that the throttle stop screw is disturbed. A slightly open throttle will make the idle unstable. Have you done throttle body service, which includes checking throttle closing, TPS calibration, cleaning, etc.
You need to reset the ECU after such services. And it wil take some time to learn idling.
A dropping rpm is mostly due to bad/clogged IACV. It should spin nice and smooth.
A hard pedal could be due to binding cable or throttle plate. Make sure there is a little slack in the cable at the throttle body end.