1) If you don't want shadows, SSAO and others rendering stuff when you're in rendering mode, then don't go in rendering mode? this mode is used to see how the animation will look like when exported. Also, wouldn't updating this every N frames will make the preview looks atrocious? because if the shadows and SSAO are rendered on one frame but stay at the exact same spot on the next frame, then you would have floating shadows and SSAO, which would just be horrible to look at.
2) It's impossible. From what I understood, Mine-Imator doesn't allow polygons and the UV isn't the same as .obj UV's
3) I think if you're far enough from an object, it won't be drawn, but I'm not sure.