Dont over think it... XG Electrical systems are very simple.
It could be a fault fuel pressure reg, a faulty relay, or a faulty smart lock module. Those are the three things I'd be going after.
Eliminate the fuel pressure reg and pump, by pulling the relay and hotwiring the pump.
(whilst watching a fuel pressure gauge)
If you can force the pump to run good, then go after either the relay, or the Smart lock module.