"When it isn't turning over couldn't I run a jumper wire from my battery positive to the little wire post on the starter and if it turns over then doesn't that mean the wire harness is bad?"

By doing this you're testing the ignition switch circuit to the starter.

The starter has two circuits.

One circuit from positive battery via the thick red cable to starter and grounds it on the engine, this goes back to the negative battery via the ground cable from engine.

Another circuit from positive battery goes into the dashboard via the ignition switch, thru neutral safety switch at gear, then to the starter's little wire post (the solenoid terminal) to make it operational. This circuit also shares the same ground on engine.

BOTH circuits must be working in order for starter to function.

Amarin.