I know first-hand how hard it is to eliminate corn completely but I have to say for my DD2 it has been completely worth the effort. She never tested positive to corn on any of the tests IgE or IgG but from observation we know 100% corn is a no go. She had terrible eczema on the backs of her legs and bum, her cheeks always looked red and chapped, and even the pads of her feet and hands were leathery and cracking - all those either went away or got significantly better when we took corn out.
There are not many prepackaged foods that are corn free (and safe with all her other limitations) but we have learned to bake many yummy treats that she loves. A few of the Larry and Luna Coconut Ice Creams are safe for my DD2. We have found some Boars Head lunch meat and Applegate farm hot dogs she does well with too, it helps to have some faster foods around. However we now cook most food from scratch so we know exactly what we are eating.
Oh and the biggy in our house is making flat bread - she can't have yeast either along with eggs, peanuts, milk, gluten, soy .. on and on. Our flat bread recipe = 1 cup garbanzo bean flour, 1/2 cup tapioca flour, 1/2 cup potato starch, 1 tsp sea salt (safe), 2 TBSP olive oil, 1 tsp guar gum, 1 cup water - blend together. The original recipe you roll out but we didn't like doing that it was too hard so we add a little bit more water so the batter is like pancake batter. Heat Olive Oil in a pan 1/2 to 1 inch of oil and pour batter into the hot oil as if you were going to cook a pancake. Wait for it to be nice and crisp turn it over cook the other side until crisp. Ok we like ours kinda crunchy but you can just cook them to be soft. My girls like flat bread plain, with jelly, with lunch meat, with black beans and fish (alla fish taco's), with refried beans, guacamole and ground hamburger. You name it anything you can think to wrap up in it. We make a whole bunch and my girls will eat them all day.
Anyway - learning to live without bread was hard for us at first so flatbread it our way to cope

I wish you good luck and I hope your son starts feeling better. Lots of hugs and support as you work through this journey.