06 Dodge Diesel Engine Shutdown Adventure-UPDATE

Check all the rubber fuel line sections, maybe they have rotted from the inside and are blocking the fuel supply to the Low pressure pump.
Worth a try..

Did they test for proper fuel pressures both high and low?

Does your truck have that small cheap electric fuel pump on the back of the fuel filter housing like our 2004.5?

If so, it could be that pump or the connections taking 12 VDC to the pump.