Now the popcorn cooking/popping is NOT my field of expertise, Al does it in this household.
I am not sure what power he uses, etc. But, I do know that he listens to the popping, and when it is sorta slowing down, as in, past the high volume pop, he turns the microwave off and grabs that bag outta there. He does not go by the timer. He does not end up with a lot of burned kernals that way.
Not sure if that will help. But, I tried!
As far as that black tank handle, I would be having the dealer look at that, it is NOT right!
Far as the hot water heater, propane, if your furnace works at switch over, and the water heater will not, hmmm??? Again, does not sound right. Are you manually switching or allowing to auto switch??