Ace, most everyone on TBN wants to help. Sometimes people that are upset add to much information about the scenario and not enough about issues with the equipment. That opens the door for emotions to enter in and not thinking clearly about the problem.
Several things are still a question for me to be able to help find a solution. Some real testing will have to be done and likely will require a dealership diagnostic computer to trace out the problem. It is possible that when the sensor plug was cut or replaced something shorted and killed part of the ECU but not likely.
One question is when the tractor ran for you when only 1 wire was connected to the sensor, did you see any warning lights on the dash?
Second question is when you had water in the fuel way back when, do you recall how many wires where on the sensor then?
Third question is did you have some change in tractor performance that prompted you to get the service done or was this just the normal scheduled service?
If all else fails, maybe dinner with the retired owner if he promises to fix your tractor would be a fair trade.

Not really!