As for the invisible parts that do not go away when you zoom the cam,,, I think it only works well when mainlight is a spot. InfiniteLight (cams) are a bit more difficult with small objects like your sphere. I just duplicated your problem. How near the specular light should be to retain its effect? I place it close to the mainlight so it does not interfere with the shadows from the mainlight. It can help sometimes with shadows and hard to light skins, too. This is just one technique in about 12,000,000 possible variances. ;) Just hoped it would make things easier for some. You can just as easily drag it to the rear and use it as a rimlight.