I haven't ever noticed any visual/image problems like some people have regarding blurry text or wake for sleep issues but I have always noticed the YPbPr issue. I have a Dell U2711 with a 2012 Retina Macbook Pro.
Hope the methods above help you fix FN key not working issues on your Dell laptop. After uninstalling the driver, restart Windows then the driver will install automatically. Expand category Keyboards, Right-click on the keyboard device and click Uninstall device from the pop-up menu.