Goerge, your boat cabin isn't hermetically sealed
If it were, you'd suffocate fairly quickly when you're aboard with all the hatches and ports closed. So plenty of warm moist air gets in without any help from a fan. You want to pull it out, not pull more in that you have to pull out, so set both your fans on exhaust when you're not there. Light definitely inhibits mildew growth, and many a boat owner--including me--has found that keeping a 60w bulb burning continuously in the cabin reduces mildew considerably and often eliminates it altogether. As for using lemon oil on the wood, it should go without saying that you have to clean the wood first. Use a mild solution of detergent, bleach and water, rinse VERY thoroughly, then wipe with undiluted bleach. When it's dry, apply lemon oil furniture polish. However, if your humidity is even higher than it is in GA in the summertime, all of the above may not be enough. I know of a couple of boat owners who keep their boats in south FL, but live elsewhere, and only get there a few times a year, so their boat stays closed up more than it's open. They cured the mildew problem by installing a dehumidifier and plumbing it to drain overboard (if it drains into the bilge, it'll only make the problem worse!). A portable unit with a drain installed in the tray that goes into the galley sink should be adequate for your boat.