First of all I would like to say that while stress is part of your husband's problem, it is by no means the biggest part. It is very difficult to handle life when your body has been traumatized.
I dislike talking about my health concerns, but I feel it is necessary to use them as they relate to what you have told me about your husband. I want him to understand that I have been where he is and that he can fully recover. I had major digestive problems. The worst being pancreatitis. I also had asthma and allergies so severe that I had to lead a very restrictive life. I have sever scoliosis, chipped vertebras and 2 herniated disc in my neck and 3 collapsed vertebra in my lower back and many other problems. Inflammation has been one of my biggest problems. However, enough said, I am sure you get the picture.
Has he done the cleanses: Colon, liver/parasite, and kidney. Multiple liver and parasite cleanses are a must.
This is most important. Eliminate all grains and sugars from his diet. He has leaky gut. Grains cause inflammation. And absolutely no junk food. Are you familiar with coconut oil and baking with coconut flour? Have you read Jordan Rubin's book "The Maker's Diet. Are you familiar with The Weston Price Foundation. I would recommend fermented foods. Can he handle kefir. If not, he needs a good probiotic. Does he take omega 3s.
If the acv bothers him at this time, I would not give it to him. Has he tried taking it in a cup of water after eating a meal. He could start with a teaspoon and work up to a tablespoon three times a day. I would recommend that he take it with equal amounts of honey, but I know he has a fungal overgrowth in his body and the honey would not be something he should have right now. Are you familiar with iodine?
He should not take a shower or a bath in chlorinated water. He should not use the hot tub if chlorine or bromine is used as a sanitizer. Are you familiar with detox baths using H202. Are you familiar with hyperbaric oxygen or ozonated water.