My relentless pursuit to cure trailer sway - the dancing TT

Once you weigh and confirm you have 10% to 15% tongue weight distribution and if the rig is still not behaving maybe you could line someone up with a different truck capable of handling your trailer - go for a tow over some road, note the way your rig handles, then hook up a comparison truck or two and go over the same road right away in the same conditions. Then maybe you will know if it is anything at all to do with your truck.

I wouldn't start spending till I figured out which vehicle is the problem.