Trump is absolutely NOT Pence's "boss".
Pence was elected by 303 Electors for Vice President appointed by the State Legislatures, his term ends at 11:59 am on January 20, 2021, and while it is not a good career move for a VP to become the enemy of the sitting President it has occurred before, and although a President (in theory) can make a VP's life hard, he can't order him around and he certainly can't fire him.
Someone on another thread was arguing that Trump should fire Pence. They actually thought that could be done.
Almost as good.......the President has the bully pulpit.
He can REQUEST the Vice President to resign, and if the VP did not resign, he could do things to humiliate him, and incite others to request his resignation.