I am so sorry to hear about your Master's health issues, there are few things as stressful as having to deal with medical problems. I can certainly understand your desire to relieve him of as much stress as possible. It sounds to me like you have a very strong relationship capable of weathering things like this, especially since you said he is so worried about the way he's treating the family. Maybe remind him that it's alright if he does make mistakes, as you will forgive him. As far as the D/s aspect goes, remember also that not every session has to be perfect or go according to plan in order for your relationship to remain strong. If you have to put certain things aside for a time until he is well, that is okay. Sometimes facing a new constraint can force you to get creative to find replacements for a missing activity, and can wind up enhancing your relationship in the end