Re: gluten free diet
I avoid the commercial gluten-free breads and pizza crusts too, and I am not autistic. They are usually made with no milk products, no eggs, no sugar, and no fats, so that they can be sold to people with a wide range of food sensitivities. They leave out all the ingredients that make bread tasty and moist. Yuccchhh!
My suggestion is to either make your own bread or go in entirely different directions for the starch part of the meal.
I make my own bread from buckwheat, teff, and rice flours. When you start using new flours without gluten, you will have to experiment to see what works for you, and which flavors your son (and you) like. The key to successfully baking with non-gluten flours is to get the dry to wet proportions right. This will take experimentation, as I said.
The other direction to go is to choose other forms of carbs. Lots of things can be spread on rice and corn crackers. Experiment with various forms of rice (long and short grains, red and white and brown), to serve with veggies or a sauce. Quinoa and Amaranth and Buckwheat and Millet have interesting flavors and are worth experimenting with. Cornbread can be made without wheat. Beans and peas have carbs as well as protein.
Bread and pizza dough have become popular because the gluten in wheat does a wonderful job of making these products easy to make and easy to eat. So we are used to seeing them everywhere and we forget that there are lots of other forms of starchy foods that are available. Looking for other options besides the ever-visible wheat has been quite an eye-opener for me. I have discovered foods that I would never have tried if I had not had to go on a gluten-free diet. I have had the opportunity to find out that I love quinoa and buckwheat but don't care for millet. Other folks find just the opposite.
I hope that you are able to find foods that your son likes.