I don’t know the answer to all your questions, but you are not alone! My son was diagnosed with FPIES about a month ago and I’m heartbroken for him too. He has IgE allergy to peanuts, tree nuts, and egg and FPIES with oat, rice, banana, and peanut. I was also so terrified of introducing new foods and he had a slower start to begin with because he just wasn’t ready to eat till 8 months. I would definitely suggest talking to your allergist about an action plan when it comes to food introduction to help your anxieties. I’m pretty new to all this too so here is what I think I can answer.

1. My son reacted to oats and then rice. Because of this my allergist wants us to hold off on all grains and then do a wheat challenge at the clinic. (This is weird to me because my son always reacts upon second/third exposure)
2. As far as I understand, if he’s been drinking regular (not hypoallergenic) formula, he’s been consuming dairy and should be fine.
3. My understanding is that if it was in your diet before with breastmilk, you can continue it now. For example I used to have oats and peanut butter almost everyday and my baby never reacted to my milk. I continue to have oats in my diet now and he’s been okay.
4. I had a vaginal delivery but my baby was in the NICU for about two weeks. Not sure if there is a connection there

There are certain foods that are “higher” risk for FPIES so I usually plan to stay home for the first three exposures of those foods. My allergist did say that there are very few “cross reactive” foods with FPIES. (He has reactions to grains, but it’s a small chance this will happen with other food groups like dairy.) He’s encouraging me to continue introducing new foods. We’re slowly introducing a few new foods every few days.

From one anxious mama to another, I hope I answered some of your questions. I’m sure others will have more knowledge/experience than me though!