I read a book a while back 'what your doctor may not have told you about IBS,' which talks about how IBS is not a specific problem people have, but a collection of problems that have similar symptoms. Often it is a collection of food intollerances. I've seen this as a reoccuring theme in books about IBS--that was just the first book I read about it in. I know that you said you have done a food journal, but maybe you should consider a serious elimination diet. Like the severity where you take it back to only eating lamb and pears (foods you would not normally eat that much of) and then slowly adding back a food at a time. It's a major commitment, but your family's situation seems disrupted enough to try it.
In the long run, we shape our lives and we shape ourselves. The process never ends until we die, and the choices we make are ultimately our responsibility.--Eleanor Roosevelt