ballbearingsandstickshift

Beware it is technically a Felony to alter the mileage on a vehicle. Just check the laws before you change anything like that.

I would try to loosen the trans mount and pick the trans up to get to that nut, rather than dropping the crossmember.

Try hooking a hose up to the inlet side of the pump and run that hose into a container with some fuel in it. if it pumps you know you have a issue behind the pump and possibly in the fuel pickup in the tank.

Ive had same type of issues getting my FRRP pump to prime. a couple time i had to put a suction after the fuel pump and once i got fuel to the pump it primed fine. Btw diesel fuel tastes horrible . Just an idea and its free to try. Im not sure how the DDRP is but my raptor dosent seem to want to pull the fuel from the tank and bleed the air behind the pump by itself.