Dead 2006 Pac 3.5 / immobilizer
 

Hello All hoping for some guidance.
I've seen this problem from many people, different variables, and no solid fix. Heres my situation. When it started the service immobilizer error message came up, warning lights lit up, no radio, no power seats, no sunroof, no speedometer etc. After looking over all grounds in engine bay and still driving the car it decided to work for no rhyme or reason after week or so. Then about a month later the service immobilizer light came back and had weird smell inside (smelled different, but think was electrical) but now the car is dead, key fob not work, half the electronics do not work ex. windows work on its respective door but cant control passenger from drivers side, no power seats, no headlights but have turn signals, cant open back lift gate, no cluster, etc, and will only click not crank.
Does it sound like a module or a wire? Do modules go out at once, or are they kind of hit and miss. I still have grounds in dash to check, and did a test and do show a short but havent narrowed down where yet (the lights for the window buttons stay lit on door).
The hit and miss feel i get makes me think wires, but after reading through all other problems could be wire, PCM, BCM... Do you know which wire to check from these modules to check operation? Also i seen a BCM fix for a Cadillac, wonder if its a similar problem with solder needing to be fixed.
There are more details but dont want to bore with long story. If need additional info to help diagnose please ask. We need our family ride and cant afford the dreaded dealership.

Any ideas?
Thanks,