Even if absolute proof of this was found beyond a shadow of a doubt, Biden would have to be impeached, convicted, and removed if he did not resign - so would Harris. That would make Nancy Pelosi the President. This is even assuming 67 Senators would vote for it and a majority of the House.
I think you're wrong about this... While Biden was being impeached he would still be in office. To undo the wrong, the rightful winner of the election would become President - and that would be Trump.
In local recounts of contested elections the true winner gets the office... when the wrong is righted.