I just had issues with my truck not starting.
It was mainly because of the cold and I was still running on WMO and the stupid GCFI got tripped so the block heater wasn't on.
You don't have fuel pressure via fuel pressure gauge?
One thing I just learned that if the battery got drained from either the cold, heater grid cycling, cranking, the fuel shutdown solenoid will not work well with low voltage when cranking. I found this out when the GFCI tripped. I had my neighbor to pull-start my truck (his truck is a Ford 6.0, no less! Haha) along with the fuel shut down solenoid tied in the up position. This was my worst one.
When I had issues with air in my fuel, I used starting fluid. If you'll use some, just a quick squirt on the BHAF, nothing more! And don't let the heater grid to cycle to avoid it from igniting the starting fluid.