Going to go back and edit the rest. Permissions are working, I just wasn't used to using command prompt and running tasks from Task Manager. I missed the tickbox for running on admin that Task Manager has when starting a task. Duh.
So it's looking like the recent update may have thrown OS files, particularly my GUI files, into a corrupted section of my hard drive. Still doing some tests through command prompt. Will do an integrity check once this sfc scan is done.
If anyone has any suggestions, I'm all ears.