f.lux can damage my video card or monitor?
when I uninstall f.lux remain files or settings to adjust it manually?
F.lux is harmless because it's not doing anything your computer isn't already designed to be able to do. In a sense, it's like asking if looking at videos and photos is harmful.
When you uninstall f.lux, it's gone. The only way to change the color temperature is through f.lux.