I am not an American. I understand this would be unconstitutional, right? Or is there an actual path to allow a third term for a president?

Yes, its unconstitutional.

However, doing something like declaring election fraud, having Vance not certify the vote, and then in chaos, remaining in power, its totally doable, granted he has legal immunity.

The things is, they are doing so much illegal shit that they know if Dems get in power, people will go to prison. So everyone around him has as large incentive to go along.