I think he should have delayed the counting until he had received assurance from the states the proper electors were the ones seated.
All 50 of the states and D.C. knew exactly when the ballots were being opened and counted, and not a single state notified him that it wanted to withdraw or amend its previously-confirmed slate of electors. Not one.
He knew there was fraud....
Pence "knew" no such thing. What he did know was that it was two months after the election, and yet not a single court in any state, either federal or state, nor any federal Circuit Court of Appeals, nor the Supreme Court, had found that sufficient fraud existed to change the winner in a state. Not
one court. Nor - as I pointed out above - had a single state provided notice that it wanted to withdraw its electors. So regardless of what anyone claims Pence "knew", he had nothing objective on which to rely except his personal say-so.
If he sent EC votes back to state legislatures for further review, 12th Amendment would’ve kicked in where GOP House of Reps would’ve voted for Trump.
And there it is!! So that seemingly tiny, very reasonable demand you had that Pence just "delay[ed] the counting until he had received assurance from the states" wasn't just a delay at all, but just a mechanism for Congress to ignore the electors.
For what it's worth, I don't think Congress would have elected Trump had it gotten to that. I think it would have elected Biden because you would have had enough Republicans realize that it would have been the end of the Republic.
That being said, I also don't think it would have gone down that way anyway. I think that if Pence had said "I'm not counting them", that Congress would have opened the ballots and counted them anyway, and declared Biden the winner.
And I think that ultimately, the Supreme Court would have backed them up on that. There is nothing in the Constitution that authorizes the VP to reject unilaterally the votes of the electoral college. Literally nothing.