Although not dealing with autism in my family, I can certainly identify with your feelings. I have tried to enjoy the "magic" moments and am trying to do what I can - while learning to be at peace with what I really can't control.
You probable know this - but there is a medical show where the lead character, a doctor, is autistic. The show is called, "The Good Doctor".
I understand that it has mixed reviews on how it deals with autism, but thought you might want to check it out.