DTW-FRA-POZ on LH then POZ-MUC-YYZ-DTW on the way back (AC over the pond) for 1504$
Might just have to miss that YYZ-DTW hopper...
Add in burning a one way rental coupon on National + 40$ in gas to get to DTW and 30€ for a r/t train ticket to Berlin and I am all set.