Agreed. I also don't see how excess exhaust in the cylinder would be hard for the engine to crank over as the OP stated.You sound too focused on the EGR valve. You don't have any EGR DTC's and it's been replaced twice.
You don't mention that you are monitoring high side rail and low side lift pump fuel pressures.
I would recommend monitoring both of these. Especially the low side fuel pressure since you have a FASS.
It could very well be a fuel system issue.
I would also recommend to monitor battery voltage with an independent voltmeter in the cab.
Monitoring these parameters would at least eliminate several variables.