Vlau you still dont have a sky cube on your sky box, one sees this from your WED screenshot.
First you must add the sky image to your WAD file or to a texture directory until it appears under "Textures". Then select the sky box and click on the sky texture and voila the texture is attached to the sky box. Your "sky mySky" what you have in your script is not needed and wont work anyway with Lite-C.
the shader tutorial shows how to apply a simple shader on block and it has shadow, it is very interesting because it means that blocks with shader effects can cast shadows