FogDucker1

Looking for some guidance on this issue, I parked my truck for 5-6 days while away on vacation and walked up to it today and the keyless entry didn't work. I thought I might have killed the battery so I got in and sure enough the battery gauge was showing it was dead (or so I thought). I tried to start it and it was cranking over strong for 2-3 seconds and then just dies like it doesn't have fuel. I got home and checked the battery and it has 12.25 volts, I tried hooking up my code reader to see if it was a position sensor that failed but the reader says no communication to the ECM. So I jumped in and all the gauges just flicker up to the bottom of the sweep so the battery shows as dead but has 12 v at it, fuel reads empty but I have over half a tank at least, the windows will not work and the power locks are also not working. I've had issues with neutral safety switches in old C10's that I've owned so I tried to shift into neutral to start it but the cluster shows all the gears but when you shift it to neutral or any other gear it doesn't show you what gear you are in (if that makes sense. Seems like a lot of things to go bad all at once so hoping I can get some direction to go in.. Is there a common fuse or ground I should be checking? Fuel pump was replaced 4-5 years ago and very little mileage since then, 2-3 month old battery after being off the road over the winter, has an aftermarket Compustar 1-way alarm installed by a good audio shop and has been in there for 10+ years with no issues.