I feel your pain. I have been where you are now. I had an 04 armada that I thought was rated to tow up to 9100 lbs, turns out I only had 800 lbs available payload. Too little for my 7000 lb tt that we bought in 2011. We traded for an 09 F250 diesel in 2012. Didn't think to check payload because we thought a diesel can tow almost anything. Wrong. It turned out our f250 only had 1500 lbs of available payload. Plenty for our current tt but not our upgrade we want so 2 weeks ago we traded for our new TV. We checked, double checked and triple checked every possible spec. The truck wasn't on the lot so we made the dealership get the other dealership to snap pics of the hitch ratings and tire loading stickers for us. We passed on 2 trucks because this revealed weaknesses that would not be capable of our next tt. We now have a truck that can handle our next tt without a doubt. We will be verifying weights at the scale on Sat but I know I have a hitch rated to 2000 lbs tongue weight and I have 4000 lbs payload per sticker which will still give us over 3000 lb payload with aftermarket add ons, family, pets, etc. I tell you this to show you the same painful journey we travelled to get us where we are today. Sadly you have discovered the Achilles heel of the 1/2 ton. It is a horrible feeling to realize you don't have as much truck as you thought you did. The good news is you know this before you bought a tt.
To figure out what you can safely tow. Get a more accurate weight with everyone (pets too), full tank if fuel and anything you plan to have in the truck when towing. Now take the trucks gvwr and subtract your scales weight to get your available payload (you understand this step already.) Next take the scaled weight and subtract it from the trucks gcwr to get your overall towing capacity. Your limiting factor will be your payload not your overall towing capacity. The loaded tongue weight must come off your available payload. So what is your loaded tongue weight? Loaded tongue weight is ideally 13-15% of the loaded tt weight. You will not know this figure until after you buy the tt. Do not shop by dry or unloaded tt Wright or dry/unloaded tongue weight. Most families tend to add 1000-1500 lbs gear into a tt (some more, some less). I advocate first time tt owners shop using the gvwr of the tt for calculations. Look for a tt gvwr less than your towing capacity. Then take 15% of gvwr to see what the worst possible tongue weight might be. Keep this below your new available payload number. Keep within these specs and you should be ok with a good wdh with integrated sway control (ie equal-i-zer or Reese dual cam) and a good proportional brake controller (ie prodigy p2 or p3). Best of luck to you.