Get the engine warm and try removing. Spray some PB blaster down there and let it sit then try again. If the engine is warm it will help a bit. Especially if you hand threaded it in there, you know it's not cross threaded. Get a bigger wrench on it and get it loose. It could be your spark plug has cracked at the insulator. Seems like a slim chance but worth looking at.
It's interesting that you are readings from the ECU are so high. Are you sure you got the constant pin correct on the ECU plug?