Not sure I see the point of tracking every tank, other than just for fun. Your averages range is from almost 21 down to 7, meaning, knowing the "range" is useless if you don't know what you are going to be doing. And if you are on regular roads, there's a gas station 5 minutes from wherever you are. If I was driving across Texas and I saw a sign that says next gas station 90 miles, I'm probably going to fill up if I'm under half a tank just to be safe.
On the fuel pump part of the equation, I get that it only needs a gallon of gas to keep it submerged, but if there is only a gallon of gas, are you getting much cooling function? You still need the volume of gas to absorb heat from the pump.
For mpg data points, My truck is probably AHC lifted a little, although I think I've brought it back close to stock. I think it was lifted when I bought it. And I'm running 34" tires, otherwise mostly stock weight. I get about 11-12mpg around town (my work commute is generally under 35mph) and I get 17.5-18.5mpg (corrected for 8% more distance covered over factory spec'd tires) on the hwy at around 75mph. When I was on my stock wheels/tires, I did about 150 miles on highway at almost 21mpg once. But that wasn't normal, not sure what was going on, maybe i had a good tailwind.