you have several questions here, so let me try and answer them one by one...
high eosinophils - not necessarily an allergic reaction, but just due to allergies - even mild allergies such as to pollen, ragweed, etc. will elevate the eosinophils. if not due to allergies, then eosinophils are likely due to being "reactionary" - in this case, the low iron levels.
bone marrow - i don't know why they are waiting, other than that they want to get a goos representative sample of your bone marrow when you haven't had any iron infusions. if your wbc count is normal, you do not likely have leukemia.
iron loss - there must be a cause. the body won't absorb it if you have a problem with your small bowel - although you say you had a GI workup. have you had your vitamin b12, d, a, and e levels looked at? they are also absorbed in the small bowel. i would also get an erythropoeitin level checked (again, while you are off iron) - this is something produced by the kidneys, and kidney problems can cause iron deficiency anemia as well.
i hope this helps,