That was never the point. It is clear that the most inhospitable place on earth is easier to settle than Mars. But the next meteor or supervolcano is a statistical certainty, and if you want to preserve the species in the long run, you need to go multiplanetary.
Yes, but I am not sure we are the Big One. I think there is an 20% probability that we go extinct in the next few hundred years, and an 80% probability that there will be significantly fewer humans on the planet than today in a hundred years from now.