@glasswiiitch
How to use S4S to find broken CC is pretty simple. Just click on the My CC button on the right. That opens a new window showing everything in your mods folder. If you keep things in subfolders, for instance, that's what you see, and you'll have to click on the subfolder to see what's inside. Then just click on an object file and new window opens with a visual of the object. You can rotate the object so you can look at it from all sides. On the right side there is a list showing the category and other details. If you've used S4S before, it's pretty much the same for objects as it is for CAS items more or less. I use it to check all my CC just to make sure it's not obviously broken before I put it in my game. It won't catch everything, but it does catch a good many things.
What you are looking for is to make sure the object will show up visually. Many broken items won't. They either won't show up at all or just not look right. It's usually pretty obvious though. You need to be aware that default replacement objects won't show up visually even if they are ok, so you have to check the items that don't give you a visual in S4S in the game. I always use a throw away save for testing things like that. Anything that doesn't show up in S4S and doesn't show up in game is broken and should be removed.
Sometimes objects may have weird looking appearances, like there is a spike that seems to go away from the object. That indicates a mesh problem, and the item should be removed. Those objects might look fine in game if they show at all but usually, they don't show up in the catalog and are broken. You're also looking to make sure the recolors work, so you should go through all the swatches on the upper right by clicking on each one. Sometimes you'll find one that does weird things. If you see anything that doesn't look right, then you can isolate it and test in game to make sure nothing is off.
Going through each item individually will take loads of time if you have a lot of CC. I suggest that you isolate the items as best as you can first and look at those in S4S first before trying to go through everything you have. But, at some point, you probably ought to look at everything you have.
A GraphicsRules.sgr file is the game file that dictates how the game appears on screen. It includes info like your graphics card, some system info, graphics settings etc. The game won't run without it. It is created when the game is installed. Normally, the file is in the game files but if your graphics performance is not what you'd like the devs gave us a way to create one of our own and that one is kept in the ConfigOverride folder in the user folder (The Sims 4) and overrides the game file. But as I understand it from @Bluebellflora your system should run just fine without a custom one. I only mentioned it as a last-ditch effort if you can't find another source for your crashing.
As for the save being corrupt, that's always a possibility but I agree with @luthienrising probably not in your case. I think the cause is broken CC. Probably build/buy based on what you've said. But it could be CAS CC too. Maybe something that you only put on one or two sims or if you have items set for random use, the game could have used it on an NPC or two and you get a crash whenever those sims enter the zone you're playing in. So if you go through all your build/buy CC and don't find the problem file, then you should go through your CAS CC.
Hope this helps.
