You are right there with the 700lb passenger estimate. If you add a backpack to the group or order a supersize meal to eat on the way you will be over.
The manufacturer has built some conservatism into their numbers as they have tested to make sure that you can operate within those limits safely for the life of the vehicle.
I see people exceeding limits all the time and it is something that I am not willing to do. Not only for legal reasons but my personal comfort level too. I grew up traveling where getting there was half the fun (we drove places on vacation instead of flying) and it is no fun to haul at the limits of the equipment.
I'm coming from a 3/4 ton diesel for 11 years prior to this and one of my decisions to "drop down" to a 1/2 ton was that I was not going to be towing much any more.
For me there's more that goes into a towing decision besides just the numbers. Wind sail is a big one as IvoryHemi mentioned above.
My personal (overly) conservative limits:
1. Anything that is over 30' is a 3/4 ton. Sway and wind sail are much better controlled with a heavier truck and longer wheelbase.
2. 5th wheel is a 3/4 ton. Heavier pin weight would probably max out payload and will put a larger strain on the rear axle. The 3/4 ton has a full-floating rear axle to better support that load in addition to beefier suspension.
3. Anything under 25' and no more than 8000 lbs GVWR can be a 1/2 ton. Small enough to stay within limits and less chance of the "tail wagging the dog".
4. 25' - 30' - by default I would use a 3/4 ton but could be a 1/2 ton. Judgement call based on GVWR and side profile.
These are just my personal comfort levels after owning 1/2 and 3/4 ton trucks (Ford F-150, Ford F-250, and now a RAM 1500). I'm sure others are willing to go a lot further but, as I said before, getting there is half the fun in my family.
If my wife was in love with that trailer I would go one of two ways with it:
1. If I had the money I would tell her that I need to trade my 1500 in and get a 2500 to safely tow "her trailer".
2. If the money wasn't there then we have to look at other trailers.
I completely understand "happy wife, happy life". I would go with "her trailer" and start looking at 2500s in my price range for "my truck".
Just my .02