This is along the right lines. The direct translation is indoor temperature on not very cold days v. indoor temperature on very cold days. We can infer that "not very cold days" are automatically warmer days and thus could be hot days.

Literally me. The first half of that sentence tripped me up so bad

In Q5, why is "those" only a reference to "novels" and not "the most successful novels?" The success of the novels feels extremely relevant to the rest of the clause. Not all novels deliver narrative suspense and character development - only the most successful ones. Thus, shouldn't the referent be the entirety of the phrase ("the most successful novels") and not just "novels?"

My best guess is that it is because "fail" is the core of the sentence - the broadest we can make the sentence. Once we add on the additional details (modifiers), the sentence narrows. I like to picture the circles previously used and visualize the scope of the sentence getting smaller and smaller as we layer on the modifiers. I then like to reverse that process to see how far we can strip back the sentence. My original answer for the predicate was "fail to kill," but that itself is still narrow and can be broadened to "fail." And that is our answer for the predicate.

You can also think of it as: what are the antibiotics failing to do? Kill. What are they failing to kill? The bacteria. In this format, you can easily see how the additional information narrows the scope of the sentence.