Even that seems very screwy? To get into a trailer that heavy you generally are looking at a fiver or a gooseneck. A properly loaded out fiver should have between 15 and 20% pin weight. So on the low end of that figure 17,000lb x .15=2550lb you are already 350lbs overweight no one or anything in the truck. At 20% or 3400lbs you would be 1200lbs over with no one or anything in the truck. If you are using a pintel hitch at 10% tongue weight or 1700lbs, now you can take maybe one or two paasengers (weight depending) and little or nothing else.
So in reality what do you have?
In reality he has a lot more payload in that truck than the 2,200 lbs he stated, but his truck is limited to a 10,000 lb GVWR because that is the limit of the Class 2B which all 3/4 ton trucks are in. Since his GVWR is maxed out to 10,000 lbs and the weight of his truck is about 7,800 lbs, then the math gives him a payload of 2,200 lbs even though the 2500 and 3500 diesel share the same frame, front axle, front suspension, rear axle, and brakes. The only difference between the two is rear suspension, and is a 500 lbs difference in GAWR with the 3500 being at 7,000 lbs RGAWR and the 2500 being at 6,500 lbs RGAWR.
Most states do not even care about the GVWR as long as you pay the licensing fee for said GVWR and your GAWR is within spec. Here in Texas, I can give my truck a higher than 10,000 lb GVWR if I pay the licensing for it which happens to be double the cost of a 10,000 lb and below truck. They do not give you tickets for going over a manufacturer's GVWR, but will ticket you if you are over what you licensed your vehicle for. However, finding a cop that would actually ticket you for that here is about about one in ten thousand. Even if you get into an accident here a lawyer cannot sue you if you are over your manufacturer's GVWR since it is GAWR that counts in the laws here and in many other states. So that 3,400 lbs you stated above is within the 6,500 lbs GAWR of his truck once you take out the 2,900 lbs for his base curb weight with a full tank of fuel.
So don't be fooled like most are in thinking these modern 3/4 diesels are actually limited to 10,000 lb GVWR. That is only for licensing, DOT FHWA classification, and EPA emissions certification.