Who said that the max would be back in the air? If SFO-YUL is a profitable route for AC, they will figure away to start flying that route shortly. This max grounding will soon show which route are the profitable for AC. The routes AC is not making money, will feel the majority of cuts.
Nothing personal here. AC currently does not have enough planes to operate its route network. My opinion (and it's only an opinion) is that SFO-YUL will be cancelled until the Max returns to service and AC will chose to route passengers thru YYZ instead.
How would you plan to look after this asap if everything is changing daily?
Well, since OP is flying SFO-YUL-MCO, I think the somewhat obvious solution is to try and get rebooked on UA/LH SFO-Europe-MCO and avoid Max routes completely. OP said they'd prefer this option anyway. I'm guessing AC might like this solution too and it will be a win for everybody.
I made an honest effort but I could be completely wrong, please offer different advice to OP if you wish, it doesn't bother me
