I'd say Yes to all
6"
4000 psi
and reinforcement.
I used boatloads of #4 (1/2") rebar and 4600 psi concrete(32mpa) IMO you can never go overboard on a concrete slab.
That being said, if they pooch the compaction then no matter what you put in the floor your not gonna be happy with the results
I put in an 18" 2speed fan with louvers in my garage, actually the fan just shipped yesterday so it will be installed once it arrives. Pumps out 3200 CFM