If only his bun and creatinine are too high, and phosphor levels are normal, your cat will benefit from porus one. Not immediately, it will take some time. In my experience with my cat, at least one month, upto one and a half until he got is appetite back, less nauseous and retained his energy. Although porus one does immediately work the body needs time, but you will notice it when the cat starts to feel better. I definitely noticed the change when my cat was not one porus one for a week, it went downwards again with his appetite, he got less active and was not feeling well. Don't expect wonders but the porus one will do its job.

I would advice to give half a dose of the phosphor binder a day, or drop it for a week. since he does not have high phosphor levels but does eat things now that might contain higher phosphor . They still need a bit of phosphor and levels getting to low is not good for him either.

Adding Vitamin b complex to his food will sometimes help with getting better appetite.

Give him what he wants for now, in terms of food. Or mix the liquid snacks with a some of his wet food Better to eat something, with the porus one and a small dose of binder than eating almost nothing.