Hi J.. I completely understand what you are going through, but the good news is that it will get better. My 2nd son (now 3years old) was diagnosed with asthma at 6 months old, and since then, we have to nebulize him religiously every night. When he has the asthma attacks it has to be every 6 hours.
To be honest with you at the beginning it was tuft, because he cried and I felt that he was suffering and feeling trap when I put the mask.
What I did was start reading when I was nebulizing him, and now he is so used to it, that when I get the nebulizer, he goes and gets a book, and he holds the mask himself. I sit him on my lap. He likes it because is a private time with Mom or Dad, where only him gets all our attention. It is part of the night time routine.
So my advice will be to find something to do with him at the same time, hear music, sing to him, or watch a video. I didn’t do the video, because I have to nebulize him before bed time, and for an everyday routine, it was more practical for us to read a book.
Good luck, thing are going to be better. Have great holydays.