As for point 2, pressure on mars is a few millibars, so not even a percent of earths atmospheric pressure, way too little to simplify construction or anything
Not strictly accurate - varies significantly with elevation, and the bottom of Hellas Planitia (which is 2300km across) is over 1% of earth's.
But your overall point stands, nowhere on the surface of mars is above the armstrong limit https://en.wikipedia.org/wiki/Armstrong_limit