I have experience doing what you plan on, as I said in an earlier post. Your payload/ability to carry an atv is limited at best. Can you do it? Yes. Should you. No.
The atv is going to be sticking way out. There is going to be a ton of weight on the rear axle. You are going to need to adjust your WD depending on if you have the atv loaded or are just towing the camper.
With my setup, I'm right at my max payload- maybe even 50 lbs over, depending on what else is in the cab. The weight of the atv is forward of the rear axle. I added rear air bags and have an WD hitch and sway bar. It tows good, but I can feel the rear end shutter. I truly believe my setup is hurting my trucks rear end. My camper is lighter and smaller then yours and the same is true of my atv. My truck bed is also longer then yours.
Honestly, I think it will tow fine- until something fails.