I asked around on the MO2 discord and the answer I got was that MO2 has no limit on size of save files, but Bethesda games have a higher and higher chance to get the save corrupted as the file size grows. I started going back through my saves and finally was able to get one from last May to reliably save and exit, slowly, all the way to desktop. It was 50,301 KB in size. Then a new SS2 NPC showed up and my save file is now 52,017 KB. But it still exits, slowly, all the way to desktop. I sacrificed V88, Nuka World, and Spectacle Island. I had only gone to Nuka World because an SS2 NPC required it for her quest. The other two I did out of boredom, but I need to keep this character usable for Chapter 3 so I can give them up. I'll figure out how to deal with that NPC if I see her again, and she still chooses Bradburton Overpass as her quest location. Or maybe I'll run like heck if I see her approaching. :D