Kore, if you attach the sun to the camera direction in the atmosphere editor, do you still get this "offset"  in the sun  placement?
About aerial perspective; this slider is provided to enlarge or shrink the skydome, depending on the size of your scene. So small values will indeed make refelctions clearer, because the skydome is at its "right" size, with little haze ( and by haze I mean the old non spectral haze), but it might make your scene flat, without depth.