With that many trips you should look into getting Nexus which includes US Global Entry.

Windsor/Toronto or Toronto/Montreal train is OK by themselves. It gets to be quite a long ride combined on one trip.

US CBP at YUL is much more bearable than US CBP at YYZ T3 unless you have Nexus.

If you have bidded the project with an all in price you should seriously consider using PD with the flight pass to control your cost/profit. Domestic transfer at YTZ is simple.