2. I think that taking revenge on a villain would not be considered morally good. It is generally thought that revenge involves a very big "stooping down to their level" component, which makes the person exacting revenge just as bad as the person who had initially wronged them. I think that not getting revenge, and rather "taking the high road" of not reciprocating and rather allowing the universe to bring some poetic justice is what would be considered by most to be "morally good". However, I think that it when a character takes down the villain not out of revenge, but rather in the name of saving themselves, another person, or society as a whole would be universally considered to be morally good.
3. I think that the overarching plot and message of Uncle Tom's Cabin goes completely over the heads of the young audiences that typically watch Mickey Mouse, regardless of the incorporation of comedy into its portrayal. The comedy allows these audiences to be able to derive enjoyment simply from the fact that they are watching a funny cartoon, without knowing the true context behind it. Because of their ignorance of the full history and consequences of slavery and subsequently Uncle Tom's Cabin, I think it would be inappropriate only in that there are images that some might want to shelter their children from until they reach a certain age, and that the message would be lost on an audience who couldn't appreciate it.