God bless you and keep you and your family safe during this time. Remember to pray for your son's safety and health. All we ever need to do is ask, if we don't ask we will not get any of His grace and healing.
Being an ICU nurse for over 16 years it is amazing how fast an asthmatic can go down the pulmonary toilet (as ICU nurses would say). The best thing is for you to get as much education from the staff and doctors as possible. They probably have some type of simple handouts to help you with your questions and concerns.
It sounds as though your son got very sick and tight with his wheezing before going to the doctor, but there is a fine line of not going to often if not needed. Hopefully you will have a nebulizer and medication to have at home that could help with future episodes.
Whatever his triggers are for the asthma need to be decreased as much as possible. If you are unsure of his triggers, then watch him closely to see if you can find out what they are so they can be avoided in the future. I'm not sure if an Allergist would be of a benefit or not, they can be great sometimes and other times just expensive.
I cannot stress enough to ask the staff to educate you as much as possible about asthma and the triggers that bring it on. Some people don't need much of a trigger and just struggle with asthma throughout their lives. He also could have just had a one time trigger and may never get into quite the same situation again.
I do pray your son gets to feeling much and recovers quickly. Just remember kids recover so much quicker and easier than we adults do he will soon drive you nuts wanting to do things you may not be ready to do.
Sorry this is so long. If you have more questions and want to talk you can email me at <<MODERATOR DELETED EMAIL>> and I would be happy to help if possible.