I tow with a 2010 Sequoia. That 5.7L isn't straining...not even a little. Its a beast, and like all but the newest turbo motors, gas engines make all their power at higher RPM's. So seeing 4k RPM is perfectly normal.
There is a common misconception that when towing with a gas engine, high RPM's is bad and the engine is working hard. Well, its working hard, but not straining. It is working as designed.
Use the tow/haul mode and let the vehicle do what it needs to do. Toss it in S mode if you want to hold gears or have more control over gear shifts.
I also use cruise control very often on long trips. I'd say 70% of all my trip miles is with cruise on. There is no reason not to.