For what it is worth I carried a 12.5' Caribou camper on a 1991 F250 for about 16 years and often towed a 21' Wellcraft V20 behind it on a 4 1/2' hitch extension (with load distributing hitch). I really should have had more truck but it got the job done. The main shortcoming that I felt when driving was marginal brakes but it had the biggest brakes Ford offered in any pickup that year. I did upgrade to bigger tires than the LT235/85/16s that came on it when they became available. And I did have the camper package and the factory overload springs. You have more truck with less camper and less boat. As long as you excersize due caution I don't think that you will have any trouble. My main concern is whether you got the slide in camper package. That is very rare on the lot. The main component in it is a rear sway bar that you could add and probably should if you don't alreay have one.
The main issue that I had was side to side sway when going over uneven ground tossing things around in the camper. The wider treadwidth of a dually would have helped some but not much. The bottom line is that when you are an eleven foot tall rig around and hit a bump on one side it is going to sway. If you do it fast food and dishes are going to be flying. My motorhome with 8.5' wide axles is better but not a whole lot and is much more prone to dropping a tire off the side of the road. I often wish that at least the front axle on it was a little narrower.
Just be one of the slower vehicles on the road, especially in turns, and you should be fine.
One more thing, I would bet that your boat trailer doesn't have trailer brakes. I would add some if it does not. You can never have too much braking.
I understand the garage issues, that was a main factor in my decision. That plus I got a good deal on a bigger camper than I even new existed when I ordered the truck.