Your question is a good one and I wished there was a simple answer. If you go to
http://saynotomsg.com/basics_list.php you will find a list of ingredients that your son should avoid. To tackle your list, though, first whey is a healthy milk byproduct. It is when they process it to create a flavor enhancer that problems evolve. Such as, Whey Protein Concentrate, Whey Protein Isolate, Whey Protein Protease, which I can't even tell you what these are other than they fall in the category of excitotoxins and are used by the food industry to cover or mask flavors they don't want you to taste.
Yeast is something we all can eat until they autoloyze it and create a flavor enhancer. Same for enzymes. The list I referred you to is a pretty good list of things that must be avoided but it is not complete. The food industry is constantly changing how they list components on their labels simply to confuse the consumer. The FDA allows them to list autolyzed yeast numerous ways but if it is a compound word you can bet they processed simple yeast into an excitotoxin.
Part of the journey you have embarked on is to become knowledgeable of labels and how companies will find ways to avoid being open with the ingredients to use.
Mick
