I'm more familiar with teens mounting a rebellion. Infants to old people act out over life's inequities, we're more aware of it with age. At six, I'm challenged to imagine which inequities or just what is driving his behavior. At six, I am certain I still believed I could will anything a way although it was mostly an illusion. Logically nebulizing or a vest treatment produces phlegm and mucus, maybe to a newly diagnosed six year old. "Here kid, breathe this, it makes you cough" 'why would I want to cough, logically coughing means I'm sick'?
At six, a year is about 20% of that child's life experience, 10% of his most recent life experience, he's had to deal with CF. Even first grade had some breaks, shouldn't CF be over by now? The other odd things are now frequent doctor visits and needle sticks that don't fix anything, and the whole stinking family is acting different. Like I'm five again, Aunts and Uncles are talking to me in baby voices. If one more person asks me how I feel..... His life, and of course you, the parents, will never be the same.
For you, he's been sick and there is a definite release in finally having a diagnosis. A number of late diagnosed (over 14+/-) especially those of us who escaped being raised with the label of CF, realize we escaped what certainly would have been a restrictive childhood. It also hasn't been lost on us the stress we spared our parents.
I have every confidence that all of this will soon resolve to make way for the next adventure. This is where I reinforce what you already know. Stress is unhealthy at the level most CFer's and CF families are constantly at. Parents and kids at least should have a mental health counselor, minister, rabbi or PCP that will help with coping mechanisms and just listening. A psychiatrist or psychologist shoud be part of a CFer's team. Parents who rely heavily on the counsel of each other threaten their relationship. This is overwhelming stuff and a CF parent who isn't overwhelmed is a smart parent who's got a professional friend to talk to. Just a suggestion.
I also agree with the premise of a contributor closer in age. This is the time, if there ever was one to treat your little six year old like an extremely mature six-going-on-ten, adult in training. Don't set up his nebulizer and clock the time, teach him how to do it. Buy him a cool watch and have him program his alarms, well somebody can. Also, these are doctor's orders, take him to the doctor for noncompliance and let the doctor explain why he needs to do this. It just might end being played in the middle. Doctors have orders and patients take them. Be sure he doesn't begin to see the doctor as a policeman or disciplinarian.
The more independent he can be in completing his daily, dailies, the less appearance of anything abnormal or unusual will cut the stress and anxiety for everyone. Many CFer's develop an overblown sense of how they are perceived by peers. This gets really tough when they become tweens and teens.
CF is accelerating his metabolism and that is done through adrenaline mostly. With two surgeries happening, you've got a sick boy who's mind is experiencing the identical reaction an anxiety or panic attack would produce. It is a fair leap for a child to have the discipline to see past what he feels and suppress the fear. My guess is he doesn't have the skills to handle all of this with grace and maturity, I've had 64 years to get good at it and I still can catch myself acting out.
Good luck,
LL