Electrical issues after car caught fire?

Okay, then power should be coming from the Engine control relay, so it might be a bad fuel pump relay. EM02 should have power while cranking which will energize the pump. I don't see in service info if there should be more than a 2 second fuel pump prime at key On. To test the fuel pump, service info states to apply battery power to the pump, so I would assume you'll only have power to the pump for 2 seconds at key On, and then while cranking. Here is the service info on pressure testing.

Yes, a new PCM needs to be programmed to the current vehicle's VIN. For example if you order a remanufactured PCM from Flagship One, (which is a used module company) they will require the vin number and preprogram the PCM to that VIN, and in cases where the module needs security system information, they will bypass the security system and it will not be active anymore, but that is more for a BCM replacement, they do other modules besides PCM/ECM. There is TSB on this as well posted below. So, this could be the issue. Sorry if I didn't remember the used PCM. We go through so many different vehicle cases a day, sometimes I forget things unless I go back through that specific folder again.
If you have a higher end scan tool, some can do programming and data transfers to new modules.
But some of the lower voltages levels you mentioned though, still seem like there might be wiring issues, you had some voltages readings around 7-8volts, that still points to possible relay or connection issues. I thought you were going to also try the old PCM again? Did that change anything at all?