NATS

With those codes and the symptoms you have plus the parts you have already replaced. Now with the ECM down. I would probably start with a break out box and see what signals are on the CAN line at the diagnostic connection. It sounds like the CAN line is either down and the signal is not getting from the BCM to the ECM or the ECM itself has failed. The ECM does not actually do anything with NATS, all of the code work is in the BCM which has to be VIN coded to the vehicle. Then you can program the keys to the new BCM.

I would verify all the fuses, disconnect the battery for about twenty minutes, then see if you reconnect it if the ECM restores com.
Do the dash or other items work? Just no start?

Have you tried putting the original BCM back in? It is possible the one you have has a problem on the CAN line and is causing the ECM to lock out. Getting the PIN from a dealer is like pulling teeth out of a shark without any tranquilizer. For this you might be able to get an automotive locksmith to look it over and see if using the PIN to alter the settings would work.

Most likely would need to be coded. I have never really tried installing one back into the same vehicle it came from after replacement.
What does the security lamp do if you turn the key?
Could you post every code and error you can pull up? I am wondering if there is a power issue between the BCM and the ECU or even into the BCM.

Okay, you know the first two are the lockout and bad key codes in the BCM because it cannot see the keys.

U1001 - Invalid or Missing Data for Primary Id - is probably 99% of the problem - Nissan has a couple TSBs for this. A common common problem is that the engine compartment and the primary ground behind the dash get corroded and the ECU has a fit because it cannot talk to the other modules due to it not knowing what ground actually is. The repair is to clean and repair the ground points.

P0183 and P0462 both relate to the fuel tank sending unit. And both can be caused by a bad ground, which is provided by the ECU.

So pull the battery cable off and clean all of the engine compartment ground points and the one behind the dash (which I believe also grounds the BCM) and see which ones go away.
Now if that ground was bad when they programmed the new BCM it may be scrambled and need to be re-flashed, but clean the grounds and see what you get first.