The states are required by the Constitution to cast their electoral votes by Dec 14th. If there are contested states and neither candidate has 270 electoral votes, the Constitution calls for a vote of the House legislature, one vote per state delegation, on January 5th when they reconvene. If all the Republican states vote for Trump, he wins. If 4 defect, Biden wins. (26 republican legislatures vs 22 Democrat)
Trump is also well aware of this too as he mentioned it in a previous rally.
http://www.youtube.com/watch?v=LCW45stUbe8&t=47m55s
Skip to 47:55 on the video to see
I am not sure you have that correct.
Here's how I think it works (but I am not sure):
Candidate needs simple majority (NOT 270) of appointed electors in Electoral College. If a state doesn't show up with electors, they are excluded from the count. (This actually happened in 1864 (i.e. during the Civil War) when the confederate states did not show up.)