Don't the 2500-3500 have the same drive train? I know there's certain years where things may differ a bit. But the 2500 has the same motor, same tranny and same brakes. It will pull and stop the same. It only has a lower rated set of rear springs. Now maybe for 2016 things are different. Tow ratings to a certain extent are based partly on gearing. Put 3.42s in and it drops. Put 4.10s in and it goes up. Same brakes, tranny, motor.
Only thing the OPs lacking is some stiffer springs. That 5er isn't some big behemoth TH that he's loading 4000lbs of gear in that's already got a 3000lb pin weight.
That 5th wheel is plenty doable if he keeps weights in check.