YUL is not my airport so someone else would be better at commenting on the workings of it. Nexus would definitely speed up the process for you at YUL CBP. Since you fly IAD/YOW often I assume you have enrolled or has special priviledges.

The distance from YUL to Parliament Hill is 180kms which is about 1.5 hours drive or less base on Canadian driving speed on 417/40. If your meeting is closer to 417 you will save more time. If you are not familiar with road signs in French a GPS would be handy.

With a carry on, meeting ending on time (Friday pm? for sure) and no acts of God it is doable.