By connecting the starter directly to the battery you ruled out a bad ignition switch. A bad ballast resistor (if you have one) would have nothing to do with whether the starter physically turns the engine or not. Symptoms of a bad ballast resistor are the engine will crank and begin to start, but will die when you release the key.
As you determined, all signs point to a bad bendix. Sometimes a good hard smack on the side of the starter housing with a wrench will coax a few more starts out of it, but that's a roadside trick to get you home, not a fix.