How about disconnecting the FPR on the outlet side, run a hose from your FPR outlet into some catch mechanism. Crank the engine and see if you have fuel to the injectors. If you do, the injectors aren't firing on cranking. If there is no fuel, the issue lies after the fuel filter and before the injectors. I tried to think thru what you have already done: Since you have confirmed fuel pressure after the filter upon cranking, and there is no fuel in the combustion chambers....problem should lie in between, yes?