upupaway's itinerary is two nested roundtrips. The airlines will not be happy if they notice it, but, as Dorian stated, you can just use two different airlines.
Empress' itinerary seems to be a roundtrip (YYZ-YYC-YYZ), plus a circle trip (YYZ-YUL-YYC-YYZ). Your most likely shot at reducing the cost will be if you can arrange the stop in YYC on Oct 18 as a connection. Then the circle trip becomes a roundtrip YYZ-YUL-xYYC-YYZ.