Alright, I appear to have finally figured out what was causing the downloads to keep looping to 0%. I came across this troubleshooting page:
https://flightsimulator.zendesk.com/hc/en-us/articles/360016844080-Download-stuck-on-packages-Install-loop-Decompressing-issues
The specific step that fixed the problem for me was "Disable Window Auto-Tuning"
A) Disable Window Auto-tuning
- In the Windows search bar, type Command and look for ‘Command Prompt’
- In the menu select “Run as administrator”
- Enter: netsh int tcp set global autotuninglevel=disabled
- Press enter
- Reboot your computer
Apparently Window Auto-Tuning can have issues with old networking gear. I use my neighbor's internet, and it is an old and crappy Arris router which is likely the culprit. I've been downloading steadily with zero loops since I changed it. Hope this helps, for what it's worth.