I love your take on the situation! not only does this explain how he learned to fight and how he lived, it also explains how he learned of the jewel and gives him a reason to watch Kikyo and the village instead of attacking as soon as he arrived like everyone else. I can also belive that Inu would become suicidle. Not only was he without friends or family, he had no hope of ever making friends or having a family. What a sad fate for a kid.