Driving from downtown Ottawa to YUL and going the speed limit along the 417/40 will take you about 1hr45 minutes with traffic flowing. Rush hour on Fridays begins earlier in Ottawa usually at around 3pm, but this week is March Break in Ontario so I'd imagine traffic will be lighter. Also the weather looks alright with a forecast high of 12C and rain. 2 hours tops and you should be at YUL.

That really sucks that you can't just fly out of YOW on Friday night. The prices on transborder business routes are truly ridiculous, even without taxes & fees.