Ok, let's look at these numbers in a very general sense...
There are many specifics that you can get focused in on, but in general, you are looking at two things...how much you can PULL and how much you can CARRY. These numbers are related, but distinct.
'Towing capacity' is a reflection of how much you can pull. We can get in to how to get that exact number if you want to later - for now, the trailer life guide says that this will be roughly 7,000 pounds for your truck. So, your trailer, gear in the truck, hitch assembly, passengers, etc... cannot exceed a total weight of 7,000 pounds. Some people (me included) like some cushion built into the weight and try to stay 10-20% below that number, which would put you in the 5,600-6,300 total amount, but that is a personal choice. With this in mind, if we use your numbers above, you are estimating 800-900 pounds of passengers and gear. The hitch will eat up more of that (50-100 pounds), so I would estimate you are in the 800-1,000 pound range of passengers and stuff in addition to the trailer - leaving you 4,500-6,000 pounds for loaded trailer weight depending on your tolerance for being close to maxed out on weight (the biggest issue there is WHERE you are towing - level roads at sea level for shorter trips, less of a problem...traversing the mountains at high altitudes where your gas engine loses power due to thin air, bigger problem!).
Now, 'payload' is the amount your vehicle can carry. This, for you, is going to be the bigger issue. You really can't know this number for sure without going to the scale, but you are likely in the 1,500 range (note that this one does not have the need for a cushion like the towing number, you can readily use 100% of your payload). Your 600 pounds of passenger weight, 200-300 pounds of gear weight, and 50-100 pounds of hitch all come off of this - leaving you 500-600 pounds of capacity for the tongue of the trailer. The trailer tongue, once loaded, will likely run at 13-15 percent of the total trailer weight, which means a 600 pound tongue limits you to a LOADED trailer weight of 4,000-4,500 pounds.
What you can see from all of this is that, for a truck like yours, payload is much more restrictive than towing capacity. Thus, my first recommendation would be to re-think loading strategies. Make sure you get a trailer that can carry most everything you want to take on your trips. Keep your gear, as much as humanly possible, in the trailer and not the truck. That 300 pounds of gear in the truck represents the tongue weight of 2,000 pounds of additional trailer - so it makes a huge difference.
So, in sum (again, with the caveat that the only real way to know is to go to a scale)...
- If you are towing on flat lands at sea level, are really comfortable towing at your max weights (if you don't have a lot of experience I wouldn't recommend it, but it's your call), AND you buy a trailer that can handle all of your gear (leaving the trailer to just passengers), a LOADED trailer of 5,500 pounds, or even a bit higher, would likely keep you within your ratings but would be pushing it.
- If you want to keep more gear in your truck, and want to have some cushion in your powertrain (for mountain passes, general comfort, etc...), you would be better advised to star in the 4,500 and under range for a LOADED trailer.
Now, on to the specific trailer you mentioned...