Check out the actual article. The entire genome is not relevant to the experiment. The entire search space in the relevant gene was explored.
I read your article. It's a fantastic, promising experiment worthy of scientific praise.
But...
It doesn't support your wild-eyed claim that "There have been very recent experiments in heat resistant bacteria in which every possible point mutation in the relevant genes was observed."
20 million does not equal 4 to the 1953rd power.