Your speculations are frightening, but they are not unreasonable. From everything that I've read regarding Donald Trump's mental state, I concur that he is definitely a narcissist - and he has only a tentative hold on reality. There are a few books newly published dealing with his sociopathic (psychopathic) mindset. Considerable discussion about which is the more prevalent--but the issue is, frankly, moot.
The narcissistic injury that Trump will experience when the election is over, and the results are clearly not in his favor, will be immense for him. He can't imagine that this would happen to him. He thinks he's invulnerable. Why would he not? He's the President, and he's a "genius", and he has "total control" of his people and thus his role as president.
The crash to earth that he will experience after discovering that he is not going to be allowed to continue in his role as president will be very hard for him to accept. (We can hope that he will try to fake his way past the emotional devastation to preserve his image and his "infallible reputation") - but it's very doubtful, I think, that he'll be able to maintain that delusion.
The future looks bleak indeed.