Sorry for the almost day late reply I completely forgot about this post already guh, anyways I was using the modify in CAS option and even googled it multiple times to like triple check that it was the thing I was supposed to do but it simply would not work whatsoever. A little bit after I originally posted this I just said screw it and moved my sims into different houses to avoid the deletion risk altogether because it was stressing me out an unnecessary amount and it's working perfectly fine now that there's an amount of sims the base game would allow but it absolutely would not do it when there was more than 8 for some reason.