I am wondering if he may actually have a bit of Autism. If so, may want to seek a nutritionist's help on that- There are every day common foods that gently chelate mercury out of the body from Vaccines and old metal fillings.
Some are raw nuts, raw pineapple, raw apples. Things like Cilantro and Chlorella also pull heavy metals, but they may be too harsh on his body unless used under professional supervision.
I like seaweeds -- brown seaweed is good. Also look into Sodium Alginate (taken from brown seaweeds)
He also needs natural mineral replenishmement (like magnesium and potassium, etc., and he needs essential oils like Krill oil , mercury tested fish oils, cold pressed olive oil, unrefined coconut oils , Flax seed oil.