Your light rotates because you're using SHIFT + Right Click. That causes your light to circle your object. To move your light without causing it to circle your object, use SHIFT + Left Click to move the light.
i'm having some issues with shading errors on my latest model, hopefully someone can shed some light.... I've got 3 pieces of geometry with one normal map, inside maya everything looks fine, but when i import as an obj i'm getting some errors (circled in red) Everything is one smoothing group prior to the bake