You should really look at the wiring between the from the fuel pump forward. Do you have a constant 12v for a few seconds at the pump when you are cranking I would guess that if you hot wired the fuel pump and then you tried to start it, you could rule out anything else but the fuel pump wiring. Your new pump and relay are probably fine despite what’s going on. I know it’s frustrating but hang in there. You’ll get it and be smarter for it.