Has anyone had/lost a cat to FIP? ( Feline infectious peritonitis )

My darling 15 month old kitty ‘Marley’ is possibly suffering from the ‘dry’ form of FIP. He has lost weight, been sleeping a lot and not eating as much the last few weeks or so. I took him in yesterday for a battery of tests and while the good news is, his fever was lower this morning after an antibiotic injection,( normally FIP fever does NOT respond to antibiotic therapy) his globulin count is very high, which is symptomatic of FIP. He is on 2 antibiotics for the next 7 days, but all his other symptoms are conducive to an FIP diagnosis. I am devastated! I have never lost a cat to FIP in all my life. Any helpful care ideas or sharings much appreciated.