I am so sorry you are going through this! When my vet thought she had ckd, he gave me a few cans of purina pro plan NF. She did not like it til I mixed in freeze dried orijen treats and weruva. I checked purina pro plan essentials and it is high in phosphorus. I found that out by reading reviews on chewyNo.She is not nauseous that bad.
My battle is getting her to eat renal wet food. RC was the first..no joy. I have spent literally a few hundred dollars on renal variety packs and prescription 24 can orders only to either toss them out or sit in my pantry. Something is in those foods that makes her think there is poison in it. I have even hidden a tiny bit under her regular food ,she goes to the bowl,sniffs and turns away! Can't see it but picked up the scent. Then if I empty and wash her bowl and give her more of the Purina she eats it. I AM EXAUSTED.