The threat though may be the best strategy Trump has left for dealing with those who are both in a position to determine his fate and risk averse, which is how those who are most comfortable with and adjusted to the status quo often are. A lot of those type people sit in Congress.
But what might start out as a game of chicken could devolve into real conflict without that ever being the actual intention. Whatever controls there may be for channeling mass passions are seldom finely tuned. Trump is too narcissistic to care about what could happen if things spin out of control as a result of his brinkmanship.
I think he would be counting on making his opposition and the legal system cave on moving forcefully against him rather than risking massive social unrest breaking out from his supporters. I doubt Trump believes that a literal massive outbreak of social unrest could succeed in keeping him in power. Of course it wouldn't if it ever came to that, but I suspect he thinks if he raises the stakes high enough "responsible doctors will rule out surgery rather than risk severe complications."
I think Trump is guilty as sin and there is absolutely no way he can win and be vindicated through normal legal and constitutional channels. So what is he left with? Forcing politicians to reach a decision more favorable to him for reasons other than the question of guilt or innocence. I think that kind of blackmail strategy by Trump will ultimately fail also, but I predict a very rocky road before it finally does.