The pattern you say is likely the fuel gauge got hit with full voltage and is burnt out. Especially that the needle is hanging far left of E.
That the temp guage is ok says the engine was cold when this happened and there was enough resistance in the sender to prevent it from being damaged. Personally I would disable the ivr. if it is in the fuel gauge it needs to be disabled as well.
I had my ivr fail closed 12v to the gauges. Mt fuel sender survived because the tank was almost empty. The engine was up to temp so there was enough current flow to over heat the gauge and it sat well below L and only got up to below normal when the engine was up to temp.
My gut says a cluster pull is in your future.
A last possibility is the sender wire shorted, that would cause similar symptoms and results
