Regarding the fuel level to keep the pump cool, you do understand the fuel is being pumped THROUGH the motor, right? Yes, the pump picks up the fuel, sends it through the motor and on its way to the filter/engine.
I replaced the pump in our 2000 Four Winds one very cold day in January of 2013. Here's the pump/sender assembly:
You can see the generator pick up tube - it stops at the top of the white section on the motor. I've found through experience where this point is the 1/4 mark on the gauge.
The dark gray end is the pickup, and the white end is the discharge:
More pics of the project: Fuel Pump replacement project; Pump teardown Photo Gallery by B-N-Mac at pbase.com
I've heard the old song about not letting your fuel drop below 1/4 for that same reason, but because the fuel is being pulled through the pump, it is being cooled until there is no fuel left to pump.
I fill at 3/8 to a 1/2 just to have sufficient reserve as we cover a lot of miles between stations - simply because the stations can be more than 100 miles apart in desolate parts of the country. I have run the tank on the Four Winds down to well below a 1/4 one time, but was getting a bit nervous as we had no idea where the gauge was in respect to the actual fuel level. It didn't die, but at fill up, it took 45 gallons with a capacity of 55 so we still had some reserve.