As one who lived in Hawaii from 59-64 (lived in Aiea, went to Radford) and played guitars, banjo's and ukes (Martins and Vegas mostly) don't worry about the humidity. Forty to fifty percent is ideal and up to seventy isn't bad. You'll do more harm trying to dehumidify, which would happen more rapidly than what your Martin has gradually become accustomed to before you bought it. If it sounds good now, and the neck is holding it's set, your guitar is "home".

Try the Martin SP mediums which I use on my Martin 2K and match Rick's gauges almost exactly. Test the lemon oil on the guitars finish in a un-noticed spot before using it on your fretboard and bridge (I try the end of a Q-tip under one of the tuning gear arms in the middle two tuners for my tests). Then use a cheap paint brush to lightly paint on a thin coat over both fretboard and bridge about once a year. Clean the finished areas on the back of the neck and sound board of the overflow oil and let the rest set for about ten minutes. Then wipe it semi-dry and set aside overnight. You'll know you need to do it again when little white streaks appear in the grain of the exposed wood.

A bad sign of too much humidity (usually from not wiping down your fret board after sweating all over it, or a poor job of setting the frets) is when the wood between the frets begins to buckle up where each fret crosses the fretboard. Red oil or lemon oil prevents the sweat from being absorbed deep into the wood, and becomes more necessary as the instrument ages, and the surface finish of the fretboard is worn away by your flying fingers. Good Luck!