Hi A'shaea,
Your questions were of personal interest to me because I experience an unpleasant reaction when a certain food is consumed, and where it never occured before!

I have read that children may outgrow certain food allergies and intolerances, but those that first appear in adulthood usually remain for life. It makes sense then to always know what we are eating and drinking, by reading food labels carefully and learn to avoid common ingredient(s) causing the unpleasant reaction.
I'm not sure what is causing low ferritin stores, however a relationship between hypothyroid and ferritin exists. "A large body of thyroid patients have been surprised to discover that being hypothyroid also results in having low Ferritin." When ferritin is low, for whatever reason, it appears you must give yourself many weeks, into MONTHS, to improve the levels.
You could check out
http://www.healthcastle.com/iron.shtml for iron rich foods and iron absorption enhancers and inhibitors.
I'd love to see some good, quick recipes as well!
Tracey