I love your reasoning!
But if the house burns down the insurance company finds out they can use that to deny the claim if there is by law to much holy black in the house.
I t shouldn't be all that hard to find out how much is legal.
If the black powder ignites, how are they going to be able to accurately determine how much was in there in the first place since the evidence just went up in smoke? Maybe do a force/trajectory calculation based on where the house landed upon reentry from low earth orbit?