Help Mallow fight FIP

Mallow has always been an active kitty who ate way too much tuna. But since a week ago we started noticing he was being too calm, and not eating a lot. Because we were concerned, we went to the vet. The vet noticed his ears, eyes and tooth flesh was yellow - so she said he probably had liver problems and we should run a blood test soon. So that’s what we did. 2 days later we got the results and it wasn’t good. Mallow has either a tumor, or he has FIP. Most likely, looking at his symptoms he has FIP. Couple of days later, he still isn’t eating, force feeding isn’t really helping and we went to the animal hospital. That’s where they noticed his heart is beating too slow and he has fluids in his chest. Bills are adding up and we want to reach out for help. Mallow is not even 1 year old and the vets are not giving up on him yet, and neither are we. We wanna do everything in our power to get him through this without him being in pain. And if it is FIP, there’s still a chance we can stretch his life a little longer in a comfortable way.