That tt should be within the Canyons ability unless you load it to the max GVWR which would be tough with that much CCC available.
Every vehicle will lag towing in the mountains,especially one with a naturally aspirated engine. It needs to rev high to be in the engines' power band, don't be afraid of 4k+ rpm. Without some sort of boost (supercharger/turbo) your power will decrease with altitude. If you always tow in the mountains you should maybe consider trading it for a diesel version.
As for sway and white knuckle driving, there are things you can try to improve it. Know your actual weights to ensure you're loaded properly with sufficient tongue weight. Use a proper hitch and have it adjusted correctly. If the dealer did it you may want to readjust it. They usually don't take the time to do it properly (eyeball it) and it is usually before the tt is loaded. Air the truck tires to max.