Probably if your weight dist hitch were not on, you would be much less on the front axle. The weight on the tongue acts through the rear axle as fulcrum (your truck is the lever) and the equalizer lessens that tendency. I'd bet your hitch is pretty optimal. You can tell a lot about the loading by the drive "feel" if you are experienced. I don't expect you are using the stock P-rated tires. . . .
You aren't the first person to "overload" your truck. Take it easy, don't speed, maintain properly, keep tires at good pressure, and like most of the rest of us (the weight criminals) you will likely be fine.
Take my comments in context with others (like Tomhole, who I actually like a lot
). I wouldn't sell the truck because of this.
I also strongly encourage you to post this on RV.net, just to keep that hornet's nest going. Just so you know, if you do, they'll call you a clone of American Made, Yers To Discover, and a few other Tundra "Trolls"