First, it is sad to me that with all we know about our cars, that yours was not fixed in the first two weeks. A no crank, no start is no longer hard to diagsnose. If the engine fan runs fast with key "ON", it's the RCM. Replace it or fix it or have DJ fix it.

If the fan does NOT come on fast with key ON, it can be challenging, but it almost always boils down to:

Battery with a bad cell (battery voltages of less than about 10.5 will result in no starter engagement).
Bad Clutch interlock switch (manuals only).
Bad relay on the pulse module (REAL easy to diagnose).
Starter solenoid failure (VERY rare, in 14 years on here, I've seen it one time with the Crossfire); easy to diagnose as well.
Bad SLA (autos only, pretty common).

Pressing the relay on the pulse module will tell you a lot, the starter will engage if you do that, if it does not, check for 12 volts on the arm of the relay, if it is there, it's the solenoid/starter. If there is no voltage OR if the starter engages, you have one of the above issues. One last thing: If you, or the 'mechanic' is trying to find this without the wiring diagram in the service manual, you are wasting your time. "I can't read wiring diagrams" means you better get someone who can.

Second, consider seeing if insurance will "total" the car. If they have been chewing the wiring, you may end up tearing that car limb from limb to replace the harness - which is no longer available anwway.

How did they get in? They got in because they can, you can't stop them, you can seal the car up and they will climb the tires and FIND away, that is what they do - they are designed for this. I am interested in where the car was stored, Iv'e never heard of this happening in a garage, only uHaul places and livestock barns. And most Uhaul places (mine was stored in one for three years) are so clean and have enough poison and traps present that you need not worry.

You cant keep them out, ya gotta keep the car away from them, period.