There is another option to coming to Montreal
if you prefer a land crossing.
Landing at Platsburg's new international airport
and taking a bus or renting a car and crossing into Canada,
you can do the same on the way back.
Its not fast, but you avoid airports.
But, people at land crossing are often lot less knowledgeable
of these kind of special cases so I don't know if this is really better.
Even if they take you aside and strip search you.
Its very unpleasant, but its not the middle east
(where with such an ID I'd be really worried), they
would not find anything and have no ground to hold you.
BTW, I forgot, in Montreal, you clear US customs in Canada!!
So, your still on Canadian soil while your going through US
customs and the worse that can happen if they turn you back
is your stuck in Montreal where you can go to the US consulat and get things sorted (which should not be hard). You could even go
or ask the consulat for advice before travelling back to
US agents living in Montreal are probably not as terrible as those
at more backward airports.
Anyway, I think the chance of getting pulled is remote if you've got a surgeon's letter with you and clearly state what the deal is. What custom's agents are looking for most is lyars, no matter what's your story, if your status is legal and if your a US resident in good standing or US citizen, you've got the right of entry in the US.
I've been in the interview zone a few time at the Montreal airport because I was going to work or get interviews in the US.