I found that website that goes into detail a bit about galactic requirements, but it doesn’t cover what percentage of galaxies or solar systems are or are not capable of supporting life. Plus it doesn’t really go into detail about the earth’s requirements with things like size, an iron core, the position of the moon, etc.
It sounds as if your prerequisites are based on life as we know it; Why is an iron core or a moon necessary? Read Bill Bryson’s A Short History of Everything if you have the opportunity; it’s a great read.