I fixed the issue! I removed the hoses that were connected to my Thermostatic Air Cleaner and the hose that connected to the carburetor. I put a rubber fitting over the vacuum port on the carburetor. The car is now able to remain idling in Reverse and Drive.
I believe there was a vacuum leak from somewhere, or one of the components to the air cleaner was bad, thus creating a vacuum leak.
I inspected the choke and it was now fully open when idling, now I can adjust the mixture and idle speed properly without vacuum leaks.
