Hi Lex. Interesting but way too optimistic calculation in my opinion. There are some incredibly important factors which you forgot to mention or thought of: The chemical composition heavier elements in our part of the galaxy seems to be just right. We need heavy elements for some life supporting processes. We most likely had two neutron stars colliding about 100million years before our star was formed. This gave rise to a much richer distribution of heavier elements. I doubt this is the case in many parts of the universe. 2. All large stars and red dwarfs tends to emit burst of extremely dangerous radiation and burst of energetic particles. Its only stars like our sun which seems to be “stable” and friendly. In other words only a subset of all stars gives you a hospitable environment. Also location in the galaxy plays a role. I can imagine that being close to a galactic centre where there is a supermassive black hole which emits tons of dangerous radiation is a bad location for life. There are many other factors which are not accounted for in this calculation but ifs fair to say that space is an extremely inhospitable place. You could also argue that space exploration is quite meaningless for humans. Why? Well we will most likely never be able to even go to another star due to physical limitations and the extrem distance. And even if we could fly close to the speed of light we would never be able to leave our galaxy cluster, due to the fact that things beyond our cluster is speeding away from us. Also, radio waves from other civilizations have only reached x lightyears from when they started transmissions. Earth radio waves have only reached about 100years out in a bubble. If you consider that our galaxy is at least 100.000 light years across we have only reached a handful of stars yet. Your estimate of how likely it is that life becomes intelligent is in my opinion extremely optimistic when you see all other animals which are not.