Sadly, this is a very common thing while growing up. You make friends, and some will move on from your life to make way for new ones.
But the most important thing is, you told your friend how another person's behavior was making you feel. A true friend would have stood up for you and told the other boy to knock it off. While its good for our friends to have friends of their own, its not ok for them to disrespect one another. So as far as your friendship ending with Aaron, it might be time to let go and move on.
A spat over XBox.. its best to simply brush that off, and his threats, as it is just a way for them to be in control. Chances are, your friend is following the influence of the other boy and he will have to learn himself where those actions will lead him. So long as neither of them actually try to physically harm you, just ignore them both. The best thing about being your age is that there is always something new coming up for the other kids to talk about, so even if he does blab, it will be forgotten.
Hope that helps somewhat. =x