Ugh. :M I hate when dealers do this kind of stuff. I don't know if they are just clueless and really have no idea what a truck can tow or if they are just shysters willing to say anything to sell a camper. Either way, it's too bad that YOU are the one who will bear the consequences.
I don't think I'd be comfortable towing your rig with that truck. At the least, it's going to be a workout and probably a white-knuckle ride at times. It's not how much you can tow; it's how much you can stop. And sooner or later you will have to stop, FAST.
I'll give you the benefit of our bad experience--we once had a 30-ft Springdale, wonderful camper, everything we wanted. We towed it with a Ford Expedition, basically an F150-type. It was not fun to haul, that's for sure. But it gets worse. One day when we were coming back from Savannah, the rig got out of control. We ended up flipping 3-4 times, totally everything. We were VERY lucky to walk away with cuts, whiplash, and concussions! Afterward, we took a long look at our set-up and realized that we had too much trailer for our truck. It's a baaaad way to learn that lesson, let me tell you. And the dealer that sold us the rig? Never uttered a word against it. :M
Best of luck to you. I hope you can get this worked out in your favor.