You have certainly done your homework & the numbers that you have posted suggest that your within the margins of safe towing. There has been much talk about half ton pickups towing large TT's, and for the most part if you look at the specs everything is a ok, even Trailer Life Magazine has articles about the exact thing we are discussing and endorsing light trucks for this type of pulling.
I pull a 36ft TT with a Super Duty Ford F250 diesel. My truck weights 7500lbs & with a WD hitch & dual friction sway control sway is a non issue. I may get a little push from strong winds but never anything to worry about.
In my opinion the bigger the truck the better, just being inside the guidelines like you are is something that I personally would not be comfortable with. A heavy duty truck has bigger brakes, suspension, tires & it is a lot heavier in weight so that really helps when the tail try's to wag the dog. I know their are many who will disagree with me but this is my opinion.
