I would be comfortable with 2 hours myself; there is a connecting walkway between T3-T1 (landside), and it's not more than 10 minutes walking.

Immigration can be crowded, but I've never waited more than an hour, and under 5 minutes is more normal. Alitalia check-in closes 35mins before departure for domestic flights, but check-in and security are generally easily-navigated in T1 (easier than Alitalia web check-in most of the time ).

Also, if your luggage works for Air Canada, I'd guess it will pass muster with Alitalia too (I've rarely had issues being slightly over the carry-on limits).