In the same way as you say that people in the Philippines are "addicted" to rice, many in the US are "addicted" to wheat. Wheat is served everywhere and it in everything.
In my youth, I suffered from eczema on my face to the degree that you son's legs are affected. Wheat was the chief culprit. My mother knew this. She also read Prevention /i] magazine, whose founder, J. I. Rodale was an early (since the 1920s) proponent of wheat-free eating. Prevention was all around the house every month. My mother, as I said, knew better, but not a meal went by that bread or other wheat product was not an integral part of the meal. In my teens, I started reading Prevention on my own, cut out wheat, and have been free of facial eczema since then - about 45 years.
I am having a very negative reaction to hearing about your son's "cheat" days. Last week, you worried for his life; now, you condone his eating food that is causing him grave illness. At ten years of age, how is he getting this rice? You say his mother... and what I'm hearing is that she is poisoning her own son! If I am misunderstanding this situation, please forgive me for reacting wrongly. Maybe I do not understand your culture, but it seems to me that a wife who lets a husband have such free reign as to let him have extramarital affairs would also comply with her husband's directives about child-rearing.
I know so many children who follow special diets for various reasons (allergies, religious observance, etc.). You can expect Cush to do what is in his best interest if you and your wife support him. Make meals for the whole family that he can eat. That is a good way to start supporting him.