He will, in fact, be a disaster on every front. And I think he will eventually drag the Republican Party into the abyss along with his own reputation; the question is whether he drags the rest of the country, and the world, down with him.
.. It’s at least possible that bigger budget deficits will, if anything, strengthen the economy briefly.
.. America has a vast stock of reputational capital, built up over generations; even Trump will take some time to squander it.
.. The true awfulness of Trump will become apparent over time. Bad things will happen, and he will be clueless about how to respond; if you want a parallel, think about how Katrina revealed the hollowness of the Bush administration, and multiply by a hundred. And his promises to bring back the good old days will eventually be revealed as the lies they are.