K.K.
This may not be the same situation, but sounds close. My daughter will get a cough and at first it is only at night and progressively it moves into our day and gets worse at night; much worse. We have done allergy testing and she has nearly NO allergys, so we have determined it is a reaction to the temperature change. We have to give 2-3 breathing treatments a day when she is like this and that helps. After about 2 days and we don't have to continue the treatments. We did everything you listed that you are doing and this is the only thing that has helped (we eliminated all the other things except occasionally the vicks on her feet). We use the Xopenex in the machine.