I think we all have to get things straitened out. Stamina and Chakra has nothing to do with each other which Saukra at one point of the anime explains.

I don't know, but i'd say that Naruto incredible Stamina comes from him alone, remember the scenes where he trains like hell. Even when he trains to be better at chakra, he have to train harder since his chakra control is so bad, and because of that his stamina has become much better than others who have trained and learned quicker.

On the other hand, Kyubi chakra which we all saw also gave Naruto much of his strength back when he shared his own chakra, but that is a whole other thing. As chakra uses his chakra to restore Naruto as well as give him strength (if you noticed on Naruto's face that it healed when he summoned kyubi).