you can't adjust this if you are using SunLight System under General Tab of TexSky - the settings will adapt the Sunlight Parameters. If you change the Sun System to None on General Tab of TexSky, then you can now adjust the parameters that you have stated.
As for the other queries, im not sure about it, because on my settings, it all adjustable. maybe upgrading will do as quoted by Sir valerostudio.
Good Luck