@jcboy,
JC.
I feel for you, given I have a diabetic husky, a hush puppy that is in remission for cancer and little Miss, you know of, which prob has UTI at 17 and a cancerous lump that is OK for now...
But.
Bigsy is like Smokey a cat I saved, a cat you saved. When we save animals and you and I have that in common, they walk our path, we take them in, it would be hard to believe that we did it so that they just had someone at the end. Sheez, Missy was diagnosed with a liver disease, 10 or so years ago I was told to take her home..... pftttt. 3 months of hand feeding her, 17 next month bless her.
Without the blood test they can only speculate. But I bet he's a fighter like Missy regardless. And, I bet he feels love which seems to defeat Vets. And, and, and, eating well is the first sign that what ever, I'm not going no where... Missy still eats like a champ...
Don't forget I have a wabbit... and he uses a kitty litter and he's a good boy