About your son; what drugs was he exposed to; do you know?
From my jobs that these children have cramps, convulsions easily. Think magnesium, but I know it is difficult to get it into small children. magnesium glycinate possibly? There are also some liquid versions that taste relatively good.
Fungal issues, borax have helped a lot of kids I worked with; of course you can use capsules, sprinkled on his food. Or, like I did; dissolve a pinch of borax in table spoon of hot water, then fill up with juice, iodine, magnesium etc.
Selenium capsules, sprinkled, vit C; natrium ascorbate on his savory food, ascorbic acid on fruity drinks.
Yes, go easy on him, they are very vulnerable.