Consider adding a Nicro solar vent in the forepeak area. A 4" vent moves nearly twice the air a 3" does. Coupled with a passive exhaust vent at rear of the boat, this should provide a nice airflow. If you have 110v at hand, you may want to add a Goldenrod dehumififier.
Once I oiled my interior teak with a "natural" finish, a linseed oil and beeswax mix. What a mistake! That turned out to be mildew fertilizer! I had to wash all the interior teak with a bleach solution to clear that up.
If you coat the interior with teak oil, you'll find your teak getting darker and darker, usually not a good thing. If you use Wiemer's Lemon Oil, it won't darken your teak and it will prevent mildew. I suggest Wieman's because it contains NO silicon. If you use a lemon oil that contains silicon, you'll have big problems if you later try to varnish over the silicon.
in low humidity San Diego