I'll contest a few of these, which I thought were good.

Breviary: this was, to me, known and not uncommon. It's widely known to Catholics, but also, if you have an interest in medieval art or books, you'd likely know it too. It was one of the main types of books before the invention of the printing press. Think of an image from an illuminated manuscript, 50% chance it's from one.

Hippopotomonstrosesquippedaliophobia: it's not that you're expected to know the whole word, but they're looking for you to recognize components of it and infer the meaning from that. I knew sesquippedalian (sometimes jokingly used in "long word" contexts) so that was easy: but phobia is also easily identifiable, and hippo, from the latin root, I knew was not as obvious as the animal, but probably something like "large" (clue: the Hippodrome). So you could, even knowing only "phobia" and being able to guess "hippo", have a good basis for your choice.

Complacent and gauche: have heard both these uses, I think that's straightforwardly correct. If this was a dictionary that would, at worst, be the 2nd or 3rd definition. No complaints.

Source: I used to place in spelling bees and could've been a contender but I didn't have the discipline to study the dictionary for hours on the weekends, which is the next level.

To me, hippopotomonstrosesquippedaliophobia feels less like vocabulary and more like trivia

For explicit comparison: kinetic and metamorphosis are ~10x as common as breviary, and 10,000x as common as hippo….

See NGRAMs: https://books.google.com/ngrams/graph?content=Breviary%2CHip...