That switch sounds like it will work fine.

The one I'm using has a second circuit that's open when the switch is on. One side goes to ground through a resistor, the other side goes to the chassis terminal of the big red wire (NOT the battery side). Its purpose is to allow any remaining voltage in the chassis to "slowly" bleed to ground when the switch is opened so that the big terminal contacts do not arc. If yours doesn't have that, don't worry about it.

Cutting the field circuit is not for "safety", it's so that the car will stop. Most alternators will continue to product amperage with the battery disconnected, thus the car won't stop running when you disconnect the battery. Cutting the field circuit so voltage goes to zero and/or cutting some ECU power feed wire will ensure the engines stops running when the master turned is turned off.