Iodine will remove fluoride, bromide, mercury and arsenic and cilantro will remove heavy metals too. It would probably be a good idea to get a Iodine loading test done and a bromide test done to see how toxic he is with bromide.
http://www.naturalthyroidchoices.com
is run by a woman who not only is a thyroid cancer survivor but also has 2 kids (under the age of 12) who have been diagnosed as hypothyroid, had the Iodine loading test and bromide test done. Her son is ADHD and was very toxic with bromide. As he's becoming saturated with iodine, his ADHD is improving greatly. She gives her kids iodoral. I'd contact her at her site and ask what she recommends for such a little guy. I don't remember what the age of her kids were when she started them on iodoral. She'd crush the tablet and mix it in applesauce to get it down them. I don't know if 1/2 tab would be too much to start with or not. Don't forget to make sure he gets unprocessed salt every day to flush out the bromides.