First long distance tow, questions

First, that porpoising you felt sounds like it was a quite normal reaction you get from some roads. If the concrete expansion joints are at just the right spacing for your rig and the speed you are going you will get it. As far as I know it is impossible to eliminate it completely for every situation.

Secondly, it looks to me like your hitch is set up pretty well. You truck and trailer attitude look good and you say it tows well. I would leave it alone at least until you can get to a scale and see exactly what you setup is doing.
Barney