One would hope we would not see the "you need diesel" comments anymore, what was the point ? It was not even funny, it's old.
To the OP.
I towed almost same set up; 22 footer, 3400 dry, close to 5 k loaded with my old 2006 Ford Explorer v8 rated at 7000 as well. It did just fine.
I think all you need is some adjustments and run higher rpm when needed. I am not that familiar with the sway control setups so will not suggest anything, but maybe that's all you need to change.
And some people confuse the original Canyon with the new generation. They are close in size to the full 1/2 tons.