Q: Overheating, drop in oil pressure when coming to a stop

I would start by checking the thermostat. If this is not working correctly, the car will quickly overheat. Driving may temporarily keep the temperature down due to wind circulation, however once you are stopped this goes away, especially if the coolant is not flowing properly.

You may also have a problem maintaining oil pressure as you mention a drop when you come to a stop. As you know as engine RPM’s are higher more oil pressure is maintained and thus temporarily keeping the oil pressure up, however if there is not enough when the RPM’s come down so will the pressure.

I would check the oil pressure sending unit as well as the oil level itself to be sure:

1. You have enough oil.
   
2. the oil pressure sending unit is working properly.
   

As to the A/C, you will want to check to be sure there is enough refrigerant in the system, check the A/C relays to be sure they are coming on at the right times, etc. I would recommend having an expert from Your Mechanic coming to your home to diagnose your overheating issue and repair.