My questions in post #5 are related to going "go directly to iCloud.com" in a web browser on your Mac, not on any iDevice. I appreciate screen shots (post #6) but I don't know where they are from except for the one from an iPhone.
Question #1 is answered: Still plenty of space.
Question #2 seems to be answered: I assume you created the "MileTracker" and "Our wed...011" folders.
Questions #3 and 4 remain unanswered when accessing iCloud from a web browser on your iMac.
As for Desktop files being in iCloud, you stated back in post #2:
...I found the option for Desktop & Documents Folders. It was indeed unchecked. So it's now checked.
Did you subsequently return that setting to
UN-checked before closing System Prefs?