Yay! Glad that worked. Lots more on baseline grid here:
https://creativepro.com/tag/baseline-grid/

Wow, a file so bad that it cannot be saved to IDML? That is pretty crazy. I think what I would do is do a “binary” troubleshooting technique: delete the 2nd half of the pages and see if it works… if so, then Revert and delete the first half of the pages, etc. Or delete all the images and see if that works, etc. At some point, hopefully you’ll find the offending object.

Tip of the Week: Deleting All Images from a Document

Anyone who ever needs to do footnotes or endnotes needs to review all the scripts Peter Kahrel has created, including one for “Inline footnotes”:
https://creativepro.com/files/kahrel/indesign/footnote_inline.html

Well, this forum is primarily for Adobe InDesign users, so your question doesn’t quite fit.
However, if you want an inexpensive set of tools, you might want to look at the Affinity suite, including Draw, Photo, and Publish.