Hello Semi-acoustic,
As another Ovation player, and sometimes antiques refinisher.... (don't ask, it's my wife's business) I would try to contact the good old boys at Ovation Technical, and with the serial number of the instrument (from the tag on the inside of the body) they could likely confirm whether or not the finish is laquer.
If laquer was used, a spot repair to the finish might be effected with good results. Other finishes could require stripping and refinishing especially urethanes. If you know a good Luthier in your area, he might also be a source of information on how a repair might be done, and most will gladly give you a ballpark estimate. Earlier instruments would likely have nitrocellulose laquer rubbed into them, but in the time frame of your vintage, acrylic laquers, enamels , and urethanes started coming into wide use. Although the "lighter" finishes tended to be preferred on acoustic instruments to preserve the "acoustic" properties of the wood itself.
Do your research and ask questions... experimentation can result in a mess!
I almost forgot the other part of your question.... Humidify if your average relative humidity in your area is much below 50%, store in whatever position you want, that should not make a difference. If you have large differences in humidity and or temperature to contend with... a case softens the shock of those changes. Chances are that the crack you have was a result of a rapid increase in moisture content in the wood. The finish is not as flexible as the wood can swell in a given time frame, and I think that's why you have that darn crack!
Take Care; Doug
"what is this quintessence of dust?" - Shakespeare