I was turned off by Toms silliness. I wanted to speed through this and get to the poiny, get Jim out and move along.
Huck is feeling sinful about 'stealing' Jim and actally think less of Tom because he willing to get involved in letting Jim go. I think, as you both stated, he is just in it for the fun, just like when he tricked his aunt.
I am surprised Huck did not say something to Tom oabout the urgency of letting Jim go.
I loved that the Royalty got thier comupence and I hope they don't reappear in the story.