I am sorry for your situation.  I can honestly say that my husband has had few conversations with our endo since he works all day and I take him for doc visits.  I convey all pertinent information to him.  I can also see how powerless your former spouse may feel while your son is not in her care.  If she has always been the liason with medical personel, she now has to give up the power of knowing he is safe and healthy.  If your marriage has deteriorated to divorce, so might the level of trust, right?

My son is almost 6 and have had to inform the public school of his health and set up a protocol for emergencies.  It has been a very vulnerable feeling on my part.  If your ex-wife has always handled these things in the past, could a protocol not be set up in the same fashion as his school had to be informed?  And hasn't your son ever spent any time with his grandparents before the age of 7?  I don't mean to second guess your situation.  It is just the questions that come to mind. 

As for the stressors you have been refering to.  I think you must know that each child with CAH seems to respond differently.  Some seem to get better control than others.  My son plays soccer, was on the swim team, and played t-ball.  He has tolerated heat well, broke his leg and did fine with a 24 hour stress dose.  But if you spend time here exploring other issues, you will find that some kids are not the same.  They require many stress doses, seem to get ill quickly, are having hard times with advanced bone age, etc.  We are all trying to do the same things!  Your son may be one of the ones who have a more difficult time getting good control and really need consistent care.