Can you lock and unlock the doors with the FOB buttons? This relates back to the anti theft system.
And lets us know exactly what happened when you tried to start the car. You are missing details that are clues to what is going on. "Car did not start. (darn)" doesn't tell us anything.
Pizza guy also wants to know.
NOTED: " The shift mod is not communicating with the instrument cluster now ". This is new. you were in there yesterday and probably messed some connector up
Have you checked all the fuse under the hood and on top the RCM?
Who rebuilt the RCM?