From what you have written, it reminds me of my car two weeks ago. Popping, backfiring and finally stalling. I thought the distributor cap was cracked-(that happened before with similar symptoms) and the new cap had no effect. New coil, same. The car would drive for a while and then the backfiring started again. I checked the point gap which wasn’t opening very far and adjusted it (I did it by eye) and I replaced the condensor and all was well. I did check the carb jets but that had no effect either as they were all clear.
Larry Lewis