Whoa!! You need to slow down and calm down. Here are a few helpful words from a nurse. Brochitis and URI (upper respiratory infection) can be treated the same in some cases. They are not contagious but but since they are infections in the larger airways of the lungs, your son needs an anitbiotic. But keep in mind, bacteria can spread as it does anywhere and cause illness in someone else in another forms (i.e., stomach bugs); so make sure everyone washes their hands very well ALL the time, not just when someone in the family is sick. This is the best prevention of illness.
Now, since he has a URI AND the mold is high, his asthma will inevitably act up. Make sure you determine the differnce between a cold and the flu since the season is upon us. Colds will come on slowly and the flu will will just hit all of a sudden.
So lets go over the meds. Azithromycin is for the bronchitis and URI and the Amoxicillin is for the ear infection. Why two different antibiotics? Because the infection are two different strains of bacteria and do not respond to the same medication. The Crantex is for the congestion, which will help break the "sludge" up in his chest. Obviously the Tylenol is for his fever. The Albuterol will open up his airways when he has an acute (quick onset) of airway constriction. If he usually takes it 12 hours when he is not sick he is taking a maintanence dose, but when he is sick with bronchitis he is going to need it more often. It is shorter acting (doesn't stay in the system as long) than Singulair so he needs the singulair to decrease the constriction during the illness stage and if he takes it when he is not sick it also serves as a maintenance medication. The Zyrtec serves as a med that blocks the allergens (i.e. mold) from causing those acute attacks on his lungs so that he doesn't get sick or worse if he is already sick. As far as his eczema goes, it is getting worse because his immune system is working overtime with all the other stuff going on so there really isn't anything more you can do for it right now.
As far as your doctor or PA goes, if they cannot give you a straight answer or put things in terms you understand (as many doctors seem to do) you have two choices. 1. find a new doctor, or 2. refuse to leave until they can explain things so that you understand and have all of your questions answered. Just remember it is your responsibility to to understand, follow through and do what you can to be healthy.
I hope I helped answer your questions. Good luck.