I don't remember the torque, but I just make it moderately tight. It's got a crush-washer like spark plugs, so it can probably tolerate a fair range.

I usually pull the fuse for about 20 or 30 seconds. For all I know maybe 2 seconds is sufficient.

Any of the codes can be caused by bad wiring in the car, so now you have to chase that down. I'm at a bit of a loss because I don't know the actual definition of those codes. Like O2 signal vs the sensor preheater.

The circuit for that O2 sensor is completely different for the ULEV engine vs the F23A1. I think the sensor heater is powered from a different fuse & the signal goes to a different pin on the ECU. Be aware of that if you find some specific troubleshooting or wiring drawings. It's too bad I don't still have the Helm book for that car...