A hug is definitely in order here.
Reading thru this thread, my concern for your health is dominating my thoughts. I live in Canada and am a home owner, so I don't have a clue what you have for renting ombudsmen or whatever. There should be some authority there to go to bat for you against a bad landlord. No-one should have to live in a home where the ceiling is dripping. Both convenience and healthwise it is not good. The de-humidifier is just a band-aid to the whole thing. Is it possible to look into moving? Molds can be very dangerous to human health and if your plants keep getting them, it is a sign that they are present in the home I would think.
As for the orchids. I have read on this board, that making a drastic change in growing media (ex all moss to all bark) can be very hard on the plant. Physan should help but if the molds continue to be present in the air, then it will likely come back.
Please check out your resources for defunk landlords and what to do about the structural problem (whatever it is) to your home. Then when you don't have to deal with that anymore and can use your time and energy to deal with the orchid problem. And it might resolve itself when the home situation is resolved
Good luck to you and keep us posted. I truly sympathsize.