I suggest you go the AC route from YYG-YUL-(your US destination).

Also you can try YYZ (not YTZ). In any event you should plan at least a two hour connection at YYZ without NEXUS. YUL tends to be a little bit less busy, so as 13F said, 90 minutes should be plenty.

I suggest against YTZ. As your not traveling on a Canadian passport, lines in the US for inspection are much longer, and they tend to ask you more questions than they do at pre-clearance inspections.