Learning to Walk in Faith

Our son is now 20 months old and he has been recently identified as being developmentally delayed primarily in communication.  My husband and I started teaching our son sign language at around 4 months and by 9 months he was signing his needs consistently.  So to some degree our son has been able to communicate his wants and needs to us since that time. He also was very advanced in his gross motor skills and we had never a worry in that department.  
In regards to speech, he started saying "mama" and "dada" at around 6 months. We would hear him from his crib calling for my husband and I early in the morning on a consistent basis.
At around 14-15 months we started noticing that he was losing his signs instead of gaining them.  We initially thought that he was just being difficult because he appeared to be dealing with sleep issues as a result of teething.  But we are now thinking that may have not been the case.
He had his regular check up at 18 months and was still showing advancement in all areas aside from speech.  Our pediatrician was not alarmed at the time, and suggested we wait until 20 months to recheck the issue.  By 20 months he stopped signing everything aside from the word "more" and had started throwing wicked tantrums that would last for long periods of time.  Additionally, he no longer said "mama" and "dada" and just started saying "m" and "d".  It was as though he had lost all of the speech that he had gained and also lost his ability to understand speech.    I knew something was wrong and made another appointment with the pediatrician who suggested we do an elimination diet and also ordered some lab work to check for food allergies.  
We had  started to do an elimination diet a few months prior to all of this due to severe eczema on our son's legs.  We initially started with eliminating gluten and casein.  Since we were on the gluten free diet we purchased more gluten free products (which contain mostly corn) and noticed that our son's eczema had now spread to his back.  As a result we eliminated corn (and then eggs) from his diet about a week ago..  We noticed that the eczema was completely gone from his back, and it was also now disappearing from his legs.  Additionally we noticed an incredible difference in behavior.  Suddenly he was able to: follow directions, do puzzles, ride his push toys outside, signed new signs that he not signed before, sat and listened to stories, was far less active, and even said his first word.   Mind you, these were all skills I had been working on with him for months and was not successful in getting him to do any of these things until a few days ago.  He was suddenly a typical toddler!!!!  It was a remarkable advancement in less than a week's period of time.
Both Thursday and Friday  I went to church for two separate functions and provided an alternative snack for our son and specifically instructed the ladies not to give our son anything but what I packed for him. Unfortunately, they did not follow my directions and gave our son Cheerios.  He was a nightmare yesterday.  He slept horribly, has been throwing chronic tantrums over everything, stopped signing again, seemed to have forgotten everything he had learned the day before, understood nothing I said, and was severely constipated. .

Obviously, I am convinced that my son has some severe allergies to certain foods, and it really scares me.  It is not the allergy itself that concerns me, but the damage that could be done if someone innocently gives our son Cheerios or the like  I am thankful that I know what the issue is now, but realize that I will have to lean on God more to protect my son when he is not in my care.  Normally that would not be an issue for me, but now it will be.  Perhaps God is using this opportunity to teach me to give my son to him on a daily basis as well as to teach me to lean on Him for the wisdom I need to help our son be all that God intends for him to be.  In any case, I am learning to walk in faith, and I am sure once this is all said and done that I will come out being richer for the experience.