Hi Ina,
Cinnamon is a commonly used fungicide among orchid growers. We use it as a dust. In my experience it really works, though I can't say I have made controlled scientific tests.
I am as skeptical of new age nonsense as anyone (probably more skeptical). There is nothing unreasonable about expecting tree bark derivatives to have antifungal properties. If you live in tropical forests, one of the most strikinbg things you can observe is the great variation in decay rates of different kinds of wood. Local people are well aware of this and use only certain woods for contruction. Those woods have real antifungal properties.
Cinnamon is just one tree derivative with antifungal properties. Another is good old aspirin, based on willow trees. Orchid growers have found that aspirin reduces mold and fungus when plants are watered with a solution of it. I have found it useful and I have made some small tests which suggest it is effective.
Having said all this, it sounds like you need a serious systemic fungicide, and I would be surprised if anything less will help you...
Best,
Lou