Tongue weight is tongue weight and it goes on the tow vehicle...ALL OF IT.
Tongue weight might be tongue weight and it goes somewhere. But, it does not all go on the tow vehicle. A weight distribution hitch will redistribute about 20 percent of the redistributed weight back to the trailer axles. It is not all on the tow vehicle.
If the OP's trailer's tongue weight is around 12.5 percent of the travel trailer's weight (7500 pounds gross) the tongue weight will be around 940 pounds plus the weight of the hitch that can easily be another 75 or more pounds. So, the final number will likely be close to or greater than 1000 pounds. How much of that does the OP want to redistribute to the front axle of the tow vehicle and the trailer axles?
As far as the salesman, go find somebody else to help you. This guy has already shown he is not working for you.