One thing that a lot of people are overlooking: the next-in-line for President is Pence. Pence is a perfectly normal, sane competent-type politician. I don’t agree with most of his politics, but I couldn’t make a case that he’s incompetent or irresponsible. In fact, I think that’s why he was chosen as vice-president. For conservatives he makes an excellent alternative to the current lack of focus, and I think that if Trump were to do anything really bizarre, he would be removed from office whatever the circumstances and Pence would take over.
Keep an eye on the midterms. If it really looks like it’s going to be a disaster for the Republicans, something might happen to push Trump out – openly or quietly. Politicians like to remain in office (and continue getting donations from lobbyists) so if it looks like Trump is seriously endangering the status quo he could be in trouble. All those Republican career politicians he despises have plenty more practice at playing the game than he does.