Is there a display anywhere that gives the total fuel (in liters) carried by a TG? Or a display that gives the net fuel use per unit time or distance for a TG?
Well not exactly that but I use "Equalize Fuel".
That distributes the fuel evenly and gives you a neat percentage of fuel left on all ships in a TG.
The fuel situation (Ctrl + F12) also gives you a good overview in that exact format:
"Current Fuel: 5,300,383 / 10,000,000"
Including displaying the range with current fuel.