i've rebooked on TK IST-YUL, 2 Js, and YUL-YYZ, 1J+1Y for now, to be switched later. the itinerary netted a $150 refund, but cost $100 to change, so $50 savings
looks like this now
AC J, YYZ-YVR
AC J, YVR-ICN (turn)
AC J, ICN-PEK (stop 1)
TK J, PEK-IST (stop 2)
TK J, IST-YUL
AC J, YUL-YYZ (fiancee is booked in Y but we'll look to change it once another seat opens)
overall cost was $402 after change fees & booking fees, but could have been $300 if i booked it in one go. not a big deal tho.