@Gegahex I asked a couple of knowledgeable people for their thoughts on this thread. One note is about the info listed in your crash log: it states that the library running Sims 3 found a serious error and crashed the program, but it doesn't say why. (This is typical of crash logs.) So figuring out the why still requires some experimentation.
Please list the install location of the Sims 3.app, as in, is it in Applications, Users > your username > Applications, or somewhere else? Please also go back to Security & Privacy > Privacy, where you found the Full Disk Access settings, and open the Files and Folders settings in the same location. Check all the boxes for both Origin and Sims 3, restart your computer, and test.
Also, please let me know whether Origin or Sims 3 is listed in the Accessibility settings in the same location. I'm not sure whether it matters, but it was mentioned in the conversation, so it's worth checking.