I tow a 7x12 enclosed a few thousand miles a year the last two summers. It weighs 3000-3300lbs (CAT Scale weighed).
I definitely recommend trailer brakes if it's a regular occurrence like me. I have the Tekonsha P2 controller. Also, most states legally require brakes over a certain weight, not to mention it's dangerous to other drivers without.
https://www.amazon.com/Tekonsha-908...F8&qid=1477419383&sr=1-1&keywords=tekonsha+p2
I'm towing with the auto 4runner. I installed a transmission cooler, and have temperatures under 180F most of the time. Before the cooler, above 200F was common, so I installed it ASAP.
I have 906 rear springs like you; they're perfect. Usually level, or just below, once trailer is hooked up. I've not yet felt the need for a Sway and weight distribution hitch, but that may be different depending on your trailer (wind profile, load balance, etc). I have mine balanced pretty well. 10-15 percent tongue weight. Towards 15% I found is usually better for control.
You will need to drive with O/D off.
Going uphills, you have to anticipate. Often you will have to floor it, and even then the speed (this is on highways) may decline depending on the hill. On flat or slight inclines, I have no problem holding 65mph. It can do 75mph on flat land also.
I average 9mpg - 11mpg.