I think you're making a pretty significant error and leap in logic in assuming that any vote that is not the "critical" vote (or threshold deciding vote) is irrelevant. That's your definitional issue, not mine.
First past the post voting in this country means that there are structural factors that tend to narrow the field to two realistic candidates. Otherwise you get vote splitting and a strengthening of whichever party the third party "spoiler" candidate is actually least aligned with. We've seen this play out in this country so many times I can't believe it even needs to be explained.
No single vote among those two columns is the "threshold vote" even in an election decided by a single vote, because it's impossible to know the vote counts in advance in a freely held and anonymized election. Instead every vote is added to the accumulation of votes that goes towards getting "past the post." Even in an election decided by a single vote any individual vote in that pile added to the accumulation required to win - not just the final vote cast.
As practical matter, under the system as it currently exists, all the rules strongly favor pooling into two lanes because those are the two that can actually win. Every other vote effectively is null. Sorry. That's the way it is. You wasted your vote in 2016 other than I guess it made you feel better. I wasted my vote in 2012 basically just to say I voted for a female candidate. That was dumb too.
There's always a handful of exceptions to what I'm describing above that require regional explanations of local voting patterns. Lisa MurKowski's write-in campaign probably being the best example. But in the presidential election I feel very comfortable with the above until proven wrong.
