Hi, unfortunately I currently don't have any way to test anything on Linux and I don't really want to update this skin myself anymore. Try messing around with VLC Skin Editor and you might make it work yourself.
About the filenames - to my knowledge, it's not possible without editing some config files. Google for more information. If it's possible in VLC's native playlist, it'll definitely work in this skin as well.
Let me know if you find any solutions to your problems, I'll make sure to update the description or maybe even the skin itself.