In Québec, make sure you double check alternate roads you might want to take, most of the time they are not paved on the sides.

Route 185 until you reach th Fleuve St-Laurent.
185 will merge on either highway 20 or 132 ( your choice ). I recommend you stick on the 132, less traffic, less polution, more locals, more scenery but also less flat!

I actually routed you on googlemap: https://goo.gl/maps/csfrK

( we have this biking path crossing the whole province, some place are merged with the highway but most of it is bikepath, which is really safe, and you can also do some stealth camping very easy. )
Accueil - Carte interactive La Route Verte | Vélo Québec

I have never been biking north of montréal. Avoid Quebec City if you can ( they are douchy )

Depending on the day you come by Montréal, I would gladly invite you to a home BBQ and get some calories in your belly.!

PM me for my information if you want