Personally, I am just over the worst of the cold that you describe. Yes, I would be VERY annoyed if my doctor wouldn't see my child and, as a result, had to make costly ER visits. Especially if it looks like the cold your daughter recently had. I love my pediatrician and you should love yours too. With that said, consider finding a new doctor.
You can start doing steam bath treatments. Also, try to give him something for his cough. Robutussin w/ guaifenesin (no alcohol) may help thin the mucus and treat the cough. It sounds like his cough is pretty hacking. For my cough, Robutussin did nothing to help my cough and I had to take a prescribed, codeine cough syrup. Yes, I also had a chest x-ray to rule out pneumonia - bad cough! Hot liquids (decaf. tea with lemon) will help soothe his chest. If he does have a lot of mucus, after he has had 8 ounces of a hot beverage (preferably), and even after a steam bath, try to give him a back "cupping" massage. in his lung area. What I used to do is lay my child across my lap, while I was sitting on a sofa, have them face down and I'd work on one lung at a time. (as opposed to this video which alternates) Just a few minutes a few times a day - you don't do it hard but if you are doing it correctly, you will feel your cupped hand will slightly suction his back - kind of a bongo/percussion movement. This helps loosen mucus and keep the cough productive.
I found a video on You tube that demonstrates this.
Hope this helps.