I am so happy you got a diagnosis. My son has a similar deficancy that he *may* outgrow by age three - probably not - called selective IgA deficiancy. He is more suspectable to viruses and may also need immonuglobin shots as well - weekly. His lung involvement is not as severe as your daughters - I hope your meds work for her!
Good luck, and I don't blame you at all for being guarded!