This is precisely what a strong form of egoism cannot accept. Sometimes only a small degree of anger is appropriate; but at other times, circumstances call for great anger.
When there is too great a gap between people, friendship is impossible, and often two friends will grow apart if one becomes far more virtuous than the other. Aristotle does not mean to suggest that unequal relations based on the mutual recognition of good character are defective in these same ways.
I think so. The exact time of his departure from The Academy is disputed, but it's said that he left soon after Plato died due to his dislike of the direction that it subsequently took. But Aristotle is not looking for a defense of this sort, because he conceives of friendship as lying primarily in activity rather than receptivity.
The pleasure of drawing, for example, requires both the development of drawing ability and an object of attention that is worth drawing. True friends are friends because they care about the same thing: goodness.
The imperfect friendships that Aristotle focuses on, however, are not unequal relationships based on good character. Has he not already told us that there can be no complete theoretical guide to ethics, that the best one can hope for is that in particular situations one's ethical habits and practical wisdom will help one determine what to do?