Also, don't forget to do your final segment with a stop-over in YYZ and an onward flight to YOW in the short term future. Then cancel that segment once you've returned and use it for a future trip to that city. (You have a year from the date of issue of the ticket to use the coupon.)
You are in fact
obligated to use the coupon, so make sure you do, sometime within the year, even if you simply take the train back the same day.
It's important to fastidiously adhere to all the rules, especially given AC's recent "crack down" on things like flight coupons and upgrade certificates. I imagine throw-a-way ticketing might be in their sights in the near future.