You NEVER should buy a rental! People beat the crap out of them and rental companies don't care because they sell them with relatively low miles.
I just got my Versa back on Tuesday and I had a new VW Jetta rental for over 2 weeks and I beat the living daylights out of that thing! Flooring it when it was still cold, spinning the tires all the time, and fwd drifting! I would say a good portion of people do the same and this reduces the life of a vehicle. Therefore, buying a rental is not an intelligent choice.
As far as #3 I agree. I couldn't believe it only takes 3.3 quarts on my Versa...but a 1.6L is a very small motor to say the least.
#4 - Tire pressure isn't based on anything other than a good balance between comfort and gas mileage when applicable. I worked at Firestone Complete Autocare for 14 months so we had to know EVERYTHING about their tires and whatnot. Our store was #1 in our region for tire sales...to get an idea we recieved a load of 300-500 tires every week....and I had to unload, stack, and put up every single one. Manufactures choose their tire pressure based on a variety of things from load capacity, mileage, comfort, and tire longetivity (if they care).