You should be under 11k, close to 10 500 with 1/2 tank fuel. For sure hit a scale at a truck stop. You can actually pull onthe scales, put the truck on the front pad, tongue jack on 2nd, trailer tires on rear.
So stop and tell the scale clerk you want to quickly jack the trailer off the ball then weigh all. If not busy they won't care. So now you get truck, tongue, and trailer axle weights. A weight will cost you $20 though but worth it.
I've hit 3 scales with similar loads and have 3 very different results though too. A 700 lb total variation.