Alright so some progress, kind of. Getting matching readings from post pump and at the Schrader valve now, turns out the Schrader valve wasn't functioning properly. Discovered this when I removed it and the readings matched. Replaced it with one from one of the accessory lines that came with the fuel pressure gauge.
Also found why my reverse lights have been coming on. When the connector for the p/n switch is moved the reverse light will turn on/off. Moving individual wires does not cause the light to come on, only when the actual connector is moved. Going to get a replacement connector and see if that fixes the issue, if not I will probably end up getting a new p/n switch.
Car still not starting, not sure what to do now...