I dont see why you can buy YYZ-MAD, then BCN-LIS(stopover)-YYZ. Then you only have to get yourself between Madrid and Barecelona by train.

Be aware of course that any use of airlines such as LH/AC will cost you hundreds of dollars in fees. Not to mention, as you already discovered, AC flights will be on rouge.
How to Save Money/YQ on Aeroplan Europe redemptions