Bad O2 sensors can contribute extra heat to the system, but usually they have the opposite effect. When the ECU detects that the sensors are faulty, the engine will default to open-loop mode, which should cause a properly functioning engine to run a rich A/F ratio. This actually has the effect of cooling the combustion charge and removing more heat from the exhaust.
The fact that bank 1's plugs are white confirms your overheat condition and/or indicates a lean A/F ratio. The fact that you are getting voltage high/low error codes leads me to believe that you may not be able to trust your electronics until the source of that error is corrected, as the ECU may be having problems reading the correct/expected input from the sensors. I would suspect the alternator's voltage regulator. If overvoltage is occurring, it may actually be causing your O2 sensors to fail.
EDIT: When an engine is hot, the radiator hoses will always be "hard and hot." The system gets pressurized (by design) as water under added pressure boils at a hotter temperature than water at atmospheric pressure.
EDIT #2: Even an engine that is running lean will not usually cause the engine to overheat (on the coolant temp. gauge) if the cooling system is functioning correctly.