@HauntedBlanket, First of all, you drag your Sims 4 folder to your Desktop to preserve your Saved games, etc. This is exactly what you want to do. Your saved games will be safe on your Desktop as long as you DO NOT delete the Sims 4 on the Desktop. You want a new Sims 4 folder to generate so that if there are any corrupt files in your old Sims 4, the new one will correct it and will "reset" your game back to a vanilla game without your CC/Mods and saved games. Sometimes outdated mods/CC ARE the problem that is causing your game not to work and moving the Sims 4 allows you to troubleshoot to see where the issue is.
Once you start up the game allowing a new folder to generate, you should start a new game and play for about an hour or so to make sure there are no additional problems or that the problem you were reporting was no longer occurring. From there once you determine that your game works again, you should check the sites/blogs to make sure CC/Mods are up to date with the current patch/Content released by EA/Maxis. If the mods have been updated, you'll need to download the newest version and add it to your new Sims 4 folder.
For CC, there is no program for the Mac OS that identifies "bad" CC. What you'll need to do in that case is to manually cull the CC by adding a few pieces at a time, starting your game up and seeing if the game starts properly and if the CC shows up. If everything is ok, then the batch of CC you added is ok and you can add more in and test. If the game does not start properly, then one of the pieces you added in that batch is "bad" and will need to be removed. Again, you'll have to cull by adding only one piece at a time from your last batch, start the game up and if it works, then that piece was ok. Repeat until you have cleared your CC from old Sims 4 on the Desktop.
You can add your Saved games back in once you have cleared and cleaned out the Mods/CC and the game appears to work fine again.