It is my pleasure to report success in solving this bug thanks to help I received on reddit. Here's the part the devs need to see: for some reason, a few days ago, the game had a hiccup and copied a TON of (apparently) junk info in the JSON save file. My 6 save files after that hiccup were around 2 gigs each! The advice I received was to delete the contents of ObjectEvents[], all text inside the square brackets. Below, I will paste what I responded to that advice with.
"Success! That was the culprit. I deleted 5 of those 6 huge save files and edited the only one I cared about, deleted everything inside ObjectEvents [], which took the file from 57 MILLION lines of code down to 49 thousand lines. No, I'm not joking. Deleting all those bugged auto-added entries apparently didn't effect anything in game at all! At least not that I can see yet. New file size is down to 2 meg, and the new autosaves the game created today are that size too. Can't thank you enough partner!! I will keep an eye on my savegame folder from now on."