I think I agree with all of these, with the possible exception of the first one. I know Huck would think that this is corruption, but I'm not sure I do. The Widow is a pretty good person too.
The one thing I can think of right off that I would mention is the way that the Phelpses behave towards Jim. They are very pious Christians, very civilized. And yet they really just see Jim as this piece of property. I think Twain is trying to show how twisted that value system was by having them be like that.
I suppose you might also consider whether Tom has been corrupted by civilization. You could say that is why he never told that Jim was actually free and instead subjected Jim to his silly stuff that was supposedly helping Jim escape.