the problem ur having has nothing to do w/ a bad head gasket or coolant leak.

its all electical.

So far, I know that the driver side fan's working just like it should be.

Unplug the passenger side fan and give it direct 12v and a negative to see if it comes on. If not then replace your fan. if it does, then go to a junk yard and get a coolant temperature sensor that goes on the thermostat housing and replace that