You can, but I'm not going to suggest you "jump" battery voltage to the PCM, in any case. That may not end well. The switch has several Batt+ outputs...
Good fuel flow out the return suggests the fuel solenoid is opening, or is open by whatever means, and fuel is available for a good pump to push fuel...
It shouldn't take "hours", at all. A dozen 20 second cycles is the most I've seen. It sure seemed like hours, though. If you're getting (bubble-free)...
An air-locked pump can take quite a bit of cranking to get it up to pressure. The inlet and return fuel is the low pressure side. The injection pump...