re: Mars
All the arguments are valid and make sense!
I'd add several observations:
Before landing and walking on the Moon, NASA performed missions in LEO to test astronauts in space for up to 2 weeks, performed rendez-vous in LEO while it was going to be needed in Moon orbit, performed spacewalks in 0G in LEO while they ended up using different spacesuits on the Moon.
So yes, they trained and often in quite different conditions from those needed for the Moon.
Also, I can't imagine going to Mars without even once returning back to the Moon, beforehand.
Raoul