I had a 2010 Tundra 5.7 and towed with it for 5 years. As you know, half tons are limited by payload. My new trailer is 8500 lbs, Tundra PULLED it fine. I didn't have sufficient payload for the tongue weight, the kids, the wife and I, firewood, bikes, etc. Decided to sell the Tundra and get a heavier truck with more payload.
At 8500 lbs I was also getting about 8.9 to 9 mpg on the highway... pretty poor. My old 6500 lbs trailer allowed me 10-11 mpg highway. Plenty of acceleration, never felt I lacked braking power, never felt like I was getting pushed around by the trailer either. I had plenty of low end grunt to get moving and plenty of mid range grunt if I needed to pass someone at speed. The engine and transmission on the Tundra are very stout and certainly not the "weak link".
Properly maintained trailer brakes and a properly set up weight distribution hitch are a MUST though. Like you I had E rated tires, which helped prevent a "squishy" feel. I have an Equal-I-Zer hitch and love it. Great weight distribution and very good sway control. Never felt sway with my truck, even in the "mountains" on the East Coast where you will be towing.
If you are interested, I have a set of Firestone air bags for the Tundra for sale.
