Welcome Katy! I do think your boy could be a Savannah, he looks very similar to one of my very early F3 Savannahs who had an Egyptian Mau sire (although mine is silver and yours is a blue boy). Statistically speaking, outdoor cats have shorter lives, I believe their life expectancy is about 5 years according to some studies, so I could never encourage you to allow him out. As for his chatty nature, some cats are just more vocal than others, I don't think it has to do with his current surroundings or how he was raised.