I am in a similar situation - a condo apartment with two bathrooms, neither of which have windows. Both have fans on the light switch. I think it would be possible to have it rewired to put a separate switch for the fan and the light, but if you use the new power saving bulbs, your cost will be minimal. A dehumidifier would certainly take the humidity out. I have never heard of using salt for odors, but am very familiar with using baking soda to absorb odors. Setting an open box in the refrigerator is very effective, so I would expect it to work well in your bathroom, too.
What I have been doing is that right after a shower, I leave the door open with the fan running for five or ten minutes. That is sufficient to air out the moisture. The rest of the time I keep the doors open only a couple of inches. This allows others to know that the bathroom is available but keeps the draining energies out of sight. Remember it is, after all, the intent that goes into the action that makes the biggest effect in Feng Shui.
