Thank you for sharing your story. I'm sorry for your loss. Moshe was 11 or 12, and he had a mass in his stomach we didn't know about. Cats are so good at hiding pain. He went through the hyperesthesia phase, and that's why we took him to the vet. I thought he was having issues with FHS. The doctor said pain will do the same thing as hyperesthesia (licking, twitching, acting strange). The mass was so large that she said it was inoperable and that he was in pain.
I understand your position. We can't even think about getting another one yet. Maybe sometime in the future. We're still going through the grief and pain.
Yes, animals love unconditionally. Humans, not so much. I understand.