Hi,

It sounds like you are facing an unusual set of circumstances. I wonder if you have seen a dietician regarding your son's condition?
Formula is generally regarded as a poor way to get iron in the diet. Formula is high in iron, but it is not easily absorbed by the child's body - most of it goes to waste. And it's not really age appropriate - many children will feel like your son and not like the taste. One problem with cows milk or formula in the diet in large quantities is that it can replace other foods in the diet - children are not as hungry for the things such as red meat which are high in the type of iron that is easily absorbed. Many mothers find an iron supplement beneficial. You only have to get a relatively small amount into them.
Good luck - and feel free to share more if you want to.