Here are your parts
Replacement parts for WHIRLPOOL RBS275PDB14 | AppliancePartsPros.com
I cannot find a PF3 error but an F3 error is related to over temperature.
That the unit went into a Clean Cycle seems to indicate that you have a bad control board that is changing cycle types on it's own. And is not controlling the temperature when it does this.
Tried to use oven later and went thru pre-warm cycle, but heating elements never came on, was blowing cold air out thru vent. Could this be a thermostat problem?
Could be but I doubt it. The unit seems to be registering the oven temperature OK as it kept the door locked till it cooled off.
Also since it gave an F3 it knew it was over temperature but could not control it.
Following is a good link with info on how to check the sensor.
What may have happened is that the oven temperature rose to such a high level that it blew the thermostat (thermal cut-off) (Item 37 in Section 1).
This would kill power to the elements.
Before ripping the unit out I would try flipping the breaker off/on slowly a couple times. Often you can loose half the line without actually tripping the breaker and the elements require the full 240 volts.