OK.

The fuel level and low fuel indicators both operate off of the tank sender. The DIC fuel usage does not, and is only useful for diagnosis if the average fuel mileage and miles remaining are calculated in. If the low fuel message and fuel gage both indicate the same (low fuel message and empty on the gage), but you still have ~7 gallons in the tank, I would suspect the tank sender. While a IPC stepper motor failure isn't unusual, it doesn't look like it at this time. It should be confirmed with a scanner before throwing time and money at it.

4-5 hours to diagnosis a fuel gage issue is insane. It takes me 15 minutes or less, or maybe up to an hour if it's a real bear (wire harness damage, for example). 4-5 hours is enough time to diagnose the cause, then replace the tank sender and IPC, including a couple union breaks and a leisure lunch. Insane.