Yup, spend some time at a scale and get some "real" numbers to work with. My experience with SUVs having owned and towed with 2 of them, payload (or RAWR) will get'cha first - well before any fantasy tow rating they put on your truck.
As for trailer length some will argue shorter trailers with SUVs or pull out some old formula to calculate TV length to TT length. But no auto maker I am aware of talks to length of trailer towed. In my experience the shorter wheel base softly sprung 1/2 ton SUV don't like big tongue weights or long TTs. My last TT was a 33' Spree. We towed it with a Hensley Arrow and that settled the whole setup nicely. But prior to that with an Equal-i-zer, it was a bit unstable IMHO no matter what we did to tweak things.
