That 5700 lbs is a useless number. Actual "advertised" UVW on that model is 5790, with 1987 lb cargo capacity. That means your gross weight could be 7777 lbs. At 7500 lbs, you could have 900 lbs tongue weight. Your weight distribution hitch, weighs approximately 100 lbs.
You're probably lacking in the areas of gear ratio, horse power, and available payload.
Add the weight of all your usual passengers, the normal cargo you will have in the truck, and 1000 lbs for hitch / tongue weight. That will tell you, your minimum payload requirement. If you want a comfort zone, add some weight for that. Then shop for a tow vehicle that has both, a high enough tow rating, and, a high enough available payload.
There are some models of F150, GM 1500 series, Toyota Tundra, Nissan Titan, and Dodge 1500 series, that have payloads from 1900 to 2300 lbs. Keyword here is "some" models. A two wheel drive, with regular size cab, will have a higher payload than a four wheel drive crew cab. Some of the above mentioned models, only have 13 - 1400 lbs available payload. If you only have 1300 lbs payload, and, you have 800 lbs passengers, you only have room for 400 lbs tongue weight with a 100 lb WD hitch.
Not long ago, there was a poster who had an F150 and he assumed it had 2300 lbs payload (as advertised by Ford). Upon checking his door post sticker, he found, his specific vehicle, had only 1400 lbs available. He had a disabled passenger who required 500 lbs of wheel chair equipment. That didn't leave him much room for his 1000 lbs of tongue weight.
Do your research independently from sales people. We all know what happens when their lips are moving.
Some numbers to keep in mind:
GVWR--- Gross vehicle weight rating --- This is total weight the tow vehicle is rated for. It includes actual weight of the truck, weight of all passengers, weight of fuel, weight of any added accessories or equipment, and hitch weight from the trailer.
Payload -- Better termed as available payload -- This is the difference between GVWR and actual weight of the truck (with full fuel and driver).
Tow Capacity -- The manufacture says the vehicle is rated to tow XXXXX lbs. This is an unrealistic number. Your vehicle probably could pull that kind of weight, if, it was a sled that did nothing to affect your payload or wind resistance. A travel trailer that weighs as much as your tow rating, could have enough tongue weight to overload your payload / GVWR and it will add significant wind resistance.
