Dry weight refers to the actual real weight of the trailer as it exits the assembly plant. Sometimes listed on the data plate as the "unloaded" vehicle weight. There are often two data plates on the trailer, one outside with just max allowed weights and inside a cupboard with the total real weight as manufactured. (includes appliances etc).
Then you add the allowable carrying weight, (liquids & personal property) and you get the gross vehicle weight. So your dry + added ins cargo & liquids shouldn't add up to more than the Gross weight allowed.
The GVWR is the absolute maximum that the trailer should ever weigh when loaded. In real life with a stuffed trailer and loaded tanks, it can come very close to that.
When I said Dry weight plus 1000 lbs, I should have been clearer, that is the minimum to consider. Adding 2-3000 lbs to your real dry weight is more realistic. Especially if ANY of your tanks are even half full.
Once you have this figure, like I said, 75% of your towing vehicle's "rated" towing ability is recommended. Not only safer, but I've learned the hard way that you will kill a vehicle very fast or at least spend a fortune on repairs if you regularly exceed this! Of course a weight distributing hitch with sway bars will mitigate your results a lot.
Yes, at 10,900 lbs rated tow capacity any way you add it up for you, you're well within the 75% rule!
Even though you feel that you are towing quite well w/o a WDH, don't knock 'em until you've tried 'em. I think they are the best thing available. So much safer. Our p/ups are rated the same (mine is a '16 GMC max tow) . My trailer is close to 4000 lbs dry, so about 6000 lbs on the road. So like you I am well under my max ability, and the truck almost tows like the trailer isn't there, however the WDH prevents 90% of any sway, and keeps my headlights pointing onto the roadway instead of up in the trees!
GM/Chev shows the 10,900 max assuming a WDH.