I would have uninstalled the 531.68 and then reinstalled it for a second time. This often works for me, I have been known to install the same driver three times! When you delete shaders, you will get stuttering as the shader cache rebuilds, that’s what I have been lead to understand. I likely would have also given the driver and system a little more time. I would not have expected frame-rate drops to 5PS, I think that really does sound like a disaster for you. Pleased you found a combination that works for you. 
I have just bought the Asobo ATR, WOW it’s terrific!
All the best!
Charles