Alaska Airlines, Air Canada, and United have round-trip flights from Dallas (DFW) to Vancouver (YVR) for $259-$288 with a connection. Flights August, September, October, November, January, and February. Origin/Destination reversible. 7-day minimum stay required. No Thanksgiving dates.
Some small OTAs on Skyscanner and Google have this for about -$20-$30 cheaper when booked as two separate one-ways on two different airlines. Beware that the reason that it is cheaper is that doing it this way avoids several airport and customs taxes that you will likely have to pay at the airport.
A Carry-on bag and also a personal item is allowed for free on Alaska Airlines. You can avoid paying for seat selection by accepting the randomly assigned seat at the gate.