This ignores the other parties, which can explain most of the disparity. In Michigan, other candidates got about 1% of the vote in 12 and 5% in 16. Even if it helped Trump win, labeling them "spoilers" just ensures that our terrible system will have this happen again.
Our system stabilizes at two parties. Other parties aren't viable until/unless they hit a point where they can eat one existing party, or large parts of both. This happening will in short order kill one or both existing major parties, some brief chaos will ensue, and we'll end up with two parties again. Labeling does not cause this.
Fixing that would be great (most sensible solutions would probably also fix our massive gerrymandering problem at the same time) but is unlikely to happen any time soon.
It's guaranteed not to happen as long as you vote for the big two parties, making sure it doesn't is one of the things that gets bipartisan support.
While I agree a win for a third party likely end with the new party entrenching itself like one of the current two, that seems like the best way to get a new party devoted to fixing this to emerge.
No. They are the people saying I need to choose between them. Supporting either is not in my interest, they will not earn my vote by being slightly less abhorrent.