“what happens with those electors if the entire presidential election was faulty?”
If the electors were appointed (Constitutional terminology) in accordance with the laws of the states which they represent, then the election is not faulty, even if all nominated candidates are later disqualified. One of the purposes of the electoral college is to ensure the election of a President; they have the power to do that even if all candidates to whom they may have been pledged die or are determined to be unqualified.
“Do they simply vote regardless if there was not a single “qualified” presidential candidate on the ballot?” YES! That is exactly what they do.
“And can the USSC retrospectively call the election by the voting public null and void due to fraud?” No. The electoral process contemplates the possibility of fraud. The electors are free to choose another person who qualifies.
So, what I understood Donofrio to say in his interview was incorrect.
Now, I can say with complete certainty that Biden won't be President unless OVER HALF OF THE ELECTORS ARE COMPLETELY INSANE!