Yeah the wording is not very descriptive. I wound up going to my towing dealer (LazyDays in Tampa FL) and talked with them about it. Basically the Nissan NV 3500 is a 1 ton truck and the 870 rating is basically for the truck WITHOUT a weight distribution hitch. Once you put the weight distribution hitch on you go by that and basically you'll run into a problem of hitting the 16,000 lbs weight limit for the truck and the trailer before you hit some issue with too much weight on the hitch (at least, I did).
I wound up buying a Keystone 3290bh travel trailer that has a 8000 GVWR. We now full time in the trailer and have for two months now. I have a Blue Ox SwayPro hitch that (originally) had 1000 lbs bars on it but it caused too much issue with weight so I had LazyDays switch them to 1500 lbs bars and it has worked great with no sway and no noticeable issues with the rear of the van dragging or anything (wheel wells are level). I put the chains on link 9 (I tried 8 and there was too much sway). My total weight (at least, last time I weighed it which included a half full fresh water tank (opps)) was 16100 lbs and the trailer at 8100 - so yeah, right on the limit (or a little bit over but meh) of what I /should/ be towing.
I have now towed this trailer 4853 miles - all the way from Orlando, Florida to Maine and back to Pennsylvania (where I currently am) - even in the mountains of Vermont it towed very solid (just make sure you put the tow mode on). I have not had to get any leafs installed in the springs nor have I had to get a transmission cooler - hottest I've ever seen the transmission get was about 1/3 full on the temp gauge. I have a Tekonsha P3 brake controller set at 8.3 and I haven't touched it since we left, been fine (When the trailer was empty from factory I had it set on 7 just FYI).
Let me know if you have any questions about it, hopefully that answers anything you might be worried about or if not I'd be glad to get more specific. :)
