Oil pressure dropping when I come to a stop and goes back up when I start driving.

Is this a high mileage vehicle? It's common, The oil pressure goes up or down with rpms. I doubt your idle is adjustable. You can check and clean anything that has to with idle air system.You might be able to use an analog gage in place of oil pressure sending unit to double check oil pressure. I can't rule out a problem with sending unit? An old rule of thumb for oil pressure was 10 psi for every 1k rpms. It would be best to check the proper specs for your vehicle, which I don't have in front of me.

Most likely a worn engine/oil pump.

I had a broken throttle cable and I was getting high RPM and stalling, and I was thinking that that could also cause the fluctuation in the oil pressure gauge reading. So my question was could that cause it? The reason why is sometimes cleaning the throttle body fixes that issue. I replaced the cable, so I will see if that corrects it.