Can anyone tell me why is seems to be cheaper to buy 2 - 1 way tickets than it is to buy a 2 way ticket? And is it ok to do this or it is against some sort of airline rules?
Unless that "rules" vary significantly in Canada from the US, it's perfectly legit to book 2 one-way flights. I've done it several times, flying one airline in and another out has saved $ and/or allowed for the schedules I wanted.