Thank you for the update.
From the picture it looks like you have configured the LED properly.
Before I test everything myself, could you do the following checks for me please?
First, when you open the Pro Shift configuration screen, all the LEDs turn on. Can you confirm that the LED you want to use as a fuel indicator turns on and that it is connected to the "Aux 2" pin?
Secondly: in Simdash you can open the "View Data" form, click the menu View->Data... This form shows all the data read from IRacing. Can you check that the values related to fuel level work and are sensible?
Thank you
Cristiano