GFCF diet is a good start, but we found that you really need to eliminate all processed food, sugar, and any food that converts to sugar. Essential eating a paleo diet with many leafy greens, utilizing healthy flours to bake or make bread with.

My son was not compliant and we did not see a difference. However, we see a difference when we avoid food dyes, high fructose corn syrup and preservatives.

My son at first try did not respond to gluten-free…,but once we got rid of food allergies, built up his skills but were still dealing with tantrums and such I tried again and WOW the difference is a MUCH calmer and in control kid. He has been gluten free for nearly 2 years and on the occasion he got gluten (without my knowledge) with in an hour he is having a major meltdown no matter what else is going on (even during favorite activities like swimming)
Enzymes also helped….especially if he did get gluten I would give him enzymes and ibuprofen which helped prevent full meltdown, but still got negative moods...

I think we need to be very careful in our advice ... We are all on our own journey, discovering what works for our families.

I have heard this 1000 times, he will not eat. And we thought the same thing. Now our son eats a variety, he gets what he gets and that is it....Be strong! If he likes Almond Milk (Unsweetened I hope), try Almond flour. We make a very simple muffin recipe with Xylitol or Stevita. Took some trial and error to find the right natural sweetener for the family. All the above you are feeding him converts to sugar. You need to cut all sugar, give it time. The pain is worth the gain. I use avocado oil and fry chicken wings in it. I use a little organic mustard, Louisiana hot sauce and seas salt as the marinade. It is now his favorite food, he makes the marinade himself.