It’s a known bug in InDesign.
My (not free) add-on V-Justify (https://www.id-extras.com/products/vertical-justification/) takes care of this, and altogether gives you much more control over InDesign’s vertical justification, so you may want to give that a try!
Ariel

Our QuickResize add-on will scale an entire document + content: https://www.id-extras.com/products/quickresize

Of course, the proportions are different for the 2 sizes you mention, so there will be some margin left over…

You could use the “Create Character Style” script that comes with InDesign.

…

You will need to separate the footnote text from the main text so that they’re 2 separate stories.
However, once that’s done, we do have a new add-on that will do book layout automatically, correctly synchronizing the 2-column main text and single-column footnotes (or vice versa, or multiple columns in both or either, etc.: it’s completely flexible). For more details, please email admin [at] id-extras.com

Works fine with our Hyperlink Pro add-on: https://www.id-extras.com/products/hyperlinkpro

There’s a Free Edition available for shorter ID docs.

This might help:

Change Consecutive Paragraphs

Nope, not possible to restart footnote numbering on the same page — unless you divide the essays into two separate text frames, one on top of the other, and are okay with the last footnotes of the top text frame appearing above the title of the second essay in the bottom frame…