I would personally stick with redeeming the 65,000 directly. You will earn miles on the flights too which is nice and you can pick any flight.

You did say your schedule is flexible though and you should be able to use aa.com to find what flights have seats on AB and then call BA to book it manually. However, note that BA pricing is distance based. I am not sure if AB goes from YYZ but if, for example, you fly YYZ-JFK-TXL-MUC, you would end up paying 29,000 each way (4,500 for YYZ-JFK and TXL-MUC and 20,000 for JFK-TXL) so the savings , while there, are not as great as you may think. If you could fly YYZ-TXL-MUC that would be 24,500 each way