I liked your tweaks to the equation. But I would like to also have a factor of habitable galaxies, galactic neighborhood, etc and capable of producing life on galaxies, galactic neighborhood,  etc. This is because most estimates for habitable planets with stars, stars capable of producing life, etc are all gathered within our own galaxy. Most galaxies in the universe aren't like our's, our placement in the galaxy is very rare and abnormal, and our galactic neighborhood is very mild. Given those conditions, a galactic neighborhood good be sparse and too cold. Or very compact and unable to support life. And goes for galaxy and other astronomic abstractions.