I will deal with the weight issue first since there are good answers to it. Some dogs are naturally lean. If his ribs don't show, he doesn't have a problem. If they do show, would he eat more if you gave it to him? If so do it. For more on this, see
http://www.askmehelpdesk.com/dogs/in...tml#post254171
I have seen ''experts'' claim all Border Collies are unsuitable as pets. That may be true for some including yours. Border Collies are notorious for needing to keep busy. Is he neutered? Doing so if not already could reduce his nervous energy. He would certainly be less distracted every time a female upwind for miles comes in season. I don't know if more attention in the evening, flyball, agility, 3 hour walks, etc., would settle him down in the day time or not. You could look at doggy day care. A whole day of supervised play with other dogs should solve most of your problems.