I see you have been through a lot with your daughter's illness and her stopping eating altogether. Then I she apparently allowed herself to starve. I feel for your situation. But how then has she gained so much weight? How could she be in the 90%?
I should think that feeding her considerably less formula and allowing her to be motivated by hunger to eat should make a huge difference. Maybe she wasn't ready to respond well then, but maybe since some time has passed she could be ready now. That is what we are doing now with our 1% 16 month old, as she eats very little but knows how to eat. Your child being 90% puts you at a huge advantage! I am not a doctor and, as you know, you've got to have your doctor approve of any changes in her feedings, but i think your child can afford to be allowed to feel her hunger. It seems like everything else is in your favor! With a child who is growing so well, I'm wondering why she is still drinking formula and not cows milk (less calories and therefor less satisfying) and why she still uses a bottle (easier flow than glass or sippy cup)? I bet I would have done the same things but maybe now she could be ready for some changes. Good luck!
My daughter has the capabilities to eat. She can eat a pretzel and a french fry. However anything else she can not. She was checked for chewing and swallowing as well as any allergies that could effeect her desire to eat. We make eating fun. I have seen a food thereapist and she thinks that she has severe sensory problems. She her weight is very good since she is on formula. I have to keep her on at least 8 bottles a day. I can not put food on the table that she is at. We tried it in the bath we tried it in the bed, we try the constinceny of the high chair at the table with the family. We are big eaters and dinner time is always family time. We make her join and sit with us and talk.
If the measurements are correct, her weight is just under the 90th percentile for her age which is very good. She has to be eating or getting some nourishment to have a good weight like that. If she is not 'eating' regular food, maybe she needs to learn how to chew and swallow food. Some children just do not know how to do it and need to be taught. They need to learn how to chew and swallow food properly; it is not really an instinct behavior like sucking. Has he been evaluated on how to chew food? If not, then suggest getting him evaluated, by going to your MD, and start therapy so he can start to eat regular food. Another important aspect at meals is for the parents to RELAX. Only she starts to eat regular food, let her eat what she wants. Slowly introduce new foods, and if she does not want it, do not make a fuss over it. Let it go and try again in a few weeks. Hoped this helped you.