@NewYorkCityTM Running the game on only one CPU core is going to make things worse, not better. Instead, try an MC reset of each town where you're having issues. If the game crashes or freezes, try a reset of only the the active lot, then in the case of the inactive sims you can't evict, try reseting that lot separately too. To see the option, click on the ground of the lot and select NRaas > MC.
Removing an EP from a save that's seen it can and does corrupt the save. It doesn't always mean that the save will be immediately unplayable; problems can surface much later. And replacing missing objects has nothing to do with it—this is about data attached to sims, for example visa levels or skills or relationships. Still, if reinstalling WA isn't an option right now, we can try to fix the save. I'm just not sure it'll work.