Windows – keyboard shortcut to “unselect” in Windows Explorer

Try shift+tab that will tab in the reverse order

Have you considered using Total Commander? It's a bit different from Windows Explorer, but you can use it entirely with a keyboard, its interface is fully customizable (color scheme, font size, type and color), you have a sort of command prompt, you can create folders just by pressing F7, you can preview files with F3 (there are plugins for Total Commander that allow you to open nearly every filetype you might need, from photos to music).

You can also use it with a tree structure for folders, similar to Explorer. I use it daily at work, and it saves me from a lot of trips to the mouse :)