You probably need to have a dietician on side. or possibly a paediatric immunologist as well.
What sort of allergy testing was it? Some is reputable, some is not. Some is useful and reliable, some is not.
I've had allergy testing done which involved skin prick tests. The ones which involve a skin prick plus putting the antigen on, then reading the test after a few minutes - they are looking for B cell problems. B cells are a type of white blood cell which can trigger anaphylactic-type histamine reactions - the B cells respond to antigens and trigger an immune response which at some point involves triggering mast cells to release histamine, which is what causes hives, swelling etc.
A skin prick test which is read several days later - it's generally looking for a T-cell response. T-cells tend to not involve mast cells, they're more related to antibody reaction. When stimulated, T-cells can trigger a different immune cascade which involves activation of cytokines which can cause other symptoms of feeling unwell. Not generally life-threatening.
Other allergy tests which are less likely to be a true reflection of true allergy status - blood test, hair test, pulse test.
I remember having a fairly carefully done skin prick test looking for B-cell response, and according to the immunologist administering the test I was allergic to tomatoes. And yet - I've never had a problem with mouth (or any other part of me) swelling when I eat tomatoes. I DID tend to get a reaction to tomato plants, but only a vague itch when handling them. I WAS in the habit of eating a lot of tomatoes at the time, which I now think may have been the reason my immune system responded.
So even a reputable test gave a false positive.
You need to define the type of allergy by identifying what sort of reaction will ensue with exposure to each antigen. If anaphylaxis or urticaria is a response at all, then that antigen should be avoided and a warning placed on the child's file. A Me-alert bracelet is also a good idea. If there is any risk to the child's life, you may need to have an Epipen handy.
Allergy shots - I presume you mean desensitisation shots? I think maybe a second opinion or more research may be beneficial. I've been advised that I may need to have my antibiotic allergies dealt with similarly, but I was also told that all this would do is buy me one more chance with each antibiotic; after that, desensitisation would no longer work. I would be asking, will the shots remove his allergy completely? And permanently? Then perhaps ask the same question on a medical site online, see what they say.
If the food "allergies" are believed to be causing problems with his mood, his concentration (or other cognitive problems) then technically they are sensitivities, not allergies. The definitions I've been taught were that allergy involves histamine release. If histamine, mast cells and B-cells are not involved, then it is not allergy. Mind you, a lot of doctors are loose with their teminology and this can be confusing.
To read labels - a dietician with access to your son's file is your best bet. Frankly, with a list of allergies as long as this, I think you need to go back to preparing all meals from your own raw ingredients. You could cook a stew, for example, and KNOW that there's nothing in it except beef, tomatoes, onions, celery, wheat (for the thickening) and maybe some fresh herbs from the garden.
Things to avoid - just about all Chinese food (takeaway) because it is likely to be thickened with cornstarch and probably also contain soy. Thai food - generally contains peanuts as well as cornstarch and soy.
Labels are a matter of practice. A dietician can advise you on which brands are safe. I can't help you there because even if the product is also available in Australia, formulations can change from state to state, let alone from one country to another. In the meantime - cook from scratch. It's safer. Go through your favourite recipes and pick out the ones which don't contain any problem ingredients. Any of your recipes that use pre-packaged ingredients, leave them out too (until you know whether they're safe or not). With some recipes, you should be able to leave out a problem ingredient or make a substitution. For example, you can thicken stews or stir-fries with wheaten flour instead of cornstarch. Or you can use arrowroot.
A lot of pre-packaged whole meal foods use soy in various forms - watch out for it. "Textured Vegetable Protein" (aka TVP) is soy-based.
You will also find that most fast food will be off your list. When going out, you will need to either make a meal on the spot (such as a salad sandwich, from bought salad ingredients) or bring something for him. McDonalds are likely to tell you exactly what is in their food, but you can't count on that everywhere. (but maybe it's better in your country?)
Good luck with this one. I suspect some professional help (perhaps via a children's hospital?) is indicated here.
Marg