Can route via CLT instead of DFW for a bit more:

YYC-PHX-CLT-ATL-CLT-YYC (6449 miles @ 253 CAD ~ 183 USD = 2.89cpm) :

https://www.google.ca/flights/#searc...=ONEWORLD;eo=e

Weird scheduling but doable. Add $7 for the overnight in ATL instead of the day in PHX to make things more reasonable.

Also I think your CPM calc is a bit off. Should be more like 3.42cpm. Interesting fare for oft overlooked canuckers though.