Wow, that is a very lengthy analysis. Unfortunately, I don't believe Luke was trying to insult the Emperor by calling him "your highness." In the scene he has resigned himself to possible death and shown that he has control over his own actions. He is saying that even the threats of an Emperor will fail before the decisions of his heart.

I just believe Star Wars takes place in a fantasy world and that the address of "your highness" simply translates the notion of superiority into our language in a way that sounds cool. "Your Imperial Majesty" is clumsier in a dramatic line.