(A3) The fine-tuning results from cosmology extend in the relevant way: the viable region of parameter space does not merely shrink as we add requirements for habitability, but shrinks fast enough that the tail of the distribution is thinner than linear.
This assumption is rather underspecified; what does it mean to add requirements for habitability, and how does that translate the number of habitable (or intelligent-life-supporting) planets?
This is a strong assertion that requires justification. How much more fine-tuning does it require to get a universe where 1 of every 1000 stars has a planet that can support intelligent life than a universe where 1 of every 10^30 stars does?