I'm so sorry you're having such a hard time with this. My sister struggled for a long time with behavioural issues in her kids, before realising that they could level everything out by just avoiding colours. I'm not saying your kids are necessarily the same, but sis the hotdogs have red shells? and Poptop drinks? Red colours? Blu is also especially bad.

You may not need to avoid additives entirely, as many 'e numbers' are actually natural, and well tolerated by most sensitive kids. The trick is to learn which is which. Once you work it out, you may realise that different brands are ok, my sister's kids can eat CCs, but not Doritos, or the other way round... I forget which, but believe me, she doesn't! There are some awesome lists and reference guides for additives which really help Mum's in your circumstances. If no-one else chips on with useful info, I can ask my sister for names and authors and web addresses for you.

Note that 'health food aisle' stuff is not always very healthy either. You're better buying single ingredients, rather than any kind of processed foods.