Yes. A bad FRPS can cause a no start on a return-less fuel system.
An easy test for is to remove the intake vacuum reference line and inspect for raw gas. IF found replace the FRPS.
Just wondering about mods to this Mustang. Stock fuel pump?
Does this car have a fuel rail Schrader valve? If the FRPS isn't ruptured then try releasing all fuel pressure and then starting from zero fuel pressure.
Will the motor "hit" on a small amount of starter fluid? Note be very careful using starter fluid on a modern car. Don't use alot!!
Just wondering. Did you pull the spark plugs to find out WHAT was in the cylinders? Remember it could be fuel or coolant.
If looking for way turning the motor backwards can clear up a hydro-lock, consider that turning backwards would create a vacuum inside the cylinder. This would make any gas boil off.
Have you inspected the oil for evidence of gas?
Note, it can be risky to turn a motor over backwards. For an automatic the torque converter pump can become un-seated. Also the cams and timing chain tensioners are designed to run in one direction. This creates additional slack that could allow the chain to skip timing. Risky. Better to limit the amount of backwards turning to say 1/4 crank turn.