First question: do you have good air circulation in your greenhouse? From your description sounds like you don't. Put an oscilating fan first (non oscillating will do the job too I think at least for now), otherwise nothing else will help. Even though one side is open it might be not enough to circulate air inside if there is no wind blowing toward greenhouse door.
You dont have insects so you don't have to use insecticides, but something to get rid of mold and fungus. Probably physan 20 will work. More experienced growers might suggest something else.