I just now created a new user and notes works fine on the same Mac for that user. Also works fine on my iPhone and iCloud.com. The reason I believe it has something to do with the slash, is immediately upon renaming the folder, it crashed and hasn't worked since. At one point the folder was there, with everything after the slash in the name, excluding the slash. I've since deleted that folder. I can't recall if it was back or forward slash. Thanks for your response!

The problem is it's a folder, not a note. When I go to edit the folders to attempt to delete the offending folder, it's greyed out, meaning I can't delete it from my phone. And it doesn't even show up on iCloud.com... Is there documentation that will help me decipher the crash log? Or does that just come with experience?

Ok I just got it working by turning off notes syncing under the mail app account sync options. This is really strange, but I appreciate your helping me!