I have the 2008 model of your truck and tow a 6500lb (unloaded) trailer without any problems. Depending on the length of the trip, I'm 7500-8000lbs loaded.
If you're concerned about ratings and want to be conservative, you should focus on the payload capacity of that truck....it's very low. Toyota's payload capacity includes the driver and all fluids including fuel, but doesn't include anything else. The manual lays it out though it can be a little confusing. My guess is you're over payload capacity if your unloaded weight is > 7-7.5k lbs and you have your family in the truck.
FWIW, Toyota adopted the new SAE tow rating standard in advance of the other manufacturers...that's why their tow ratings fell across the board while the others remained the same. IIRC, all the manufacturers agreed to adopt the new standard no later than 2013 model year. I haven't checked the other manufacturers, but I'm guessing you'll see 10-20% decreases for everything when compared apples-apples.
