I'm writing my English summer reading essay, right? Microsoft Word does not agree with me.

To literally become someone other than who he really is—that is the ultimate denial of truth that Palmer Eldritch commits.

Word says that the "who" should be a "whom." I tried restructuring the sentence so I could analyze it...

The ultimate denial of truth (subject) that Palmer Eldritch commits (relative clause) is (linking verb) to literally become someone other than who he really is (???).

Anyone really good at grammar out there (I feel weird asking that on a site like this) who has some thoughts on this?

Anyway, next one:

The vast majority of people, however, are not truthful all the time, and in turn never completely trustworthy.

Word says it ought to be "is" instead of "are." Now, the majority is a single subject, I concede that, but it just sounds so awkward... I feel it's almost idiomatic to say "the vast majority of people are such and such." Should I just change it to "the vast majority of people, however, is not truthful all the time"?

Oh yes and the essay is about the quality of truth and how that relates to a character being a hero or a villain.