I’m having the same exact issue. I even uninstalled and reinstalled my game. I tried everything you did in the list and what was suggested in past forums but my game now crashes.
I also noticed cameras and photos are gone :/
okay I resolved it (for now)! I followed this visual link below on how to recover:
https://sims4.crinrict.com/eng/2014/09/resetting-the-game-to-factory-settings-without-reinstalling/
However, mid-way through, I learned my windows security was blocking a file. If you go to windows security then look at blocked history, it'll say something in the TS4.exe file was blocked (or something similar). Allow access to that file or game and saving should work again
The Sims Team