1. Overall, your plan is OK
2. 12-2 w ground, 20 amp breaker is correct
3. I like EMT (thinwall) conduit in a garage. PVC looks kind of cheap.
4. Safety switch does not need to be same size; it can be rated higher. 30 amp models are about the easiest to find and cheapest to buy (assuming less than 30 amp load). Fuses not needed here either, only disconnecting means.
Since you have a conflict in the paperwork, look at the motor nameplate for the full load current. Don't count on the instructions. As long as the motor load is around 17 amps or less, your 20 amp plan should be a go.