I totally understand your position. Its been just over 2 years since I lost my best friend Zazoo. I bought him as a gift to my girlfriend at the time, who turned into my wife, 2 kids later, 16 years later, he had a really bad seizure, couldn't walk, was a real big mess. I made the call to put him to peace and it was the hardest thing iv'e ever done. He passed in both my daughters hands, 6-8 at the time, they were destroyed, as was I. I chose to be strong for the family but I think about him everyday, he was truly a special cat, a real "buddy".
I bought him when I was 21, he was a pure bread Persian. I couldn't afford the "best" ones, he was the runt of the litter but he didn't have the "smushed" face they always have. He was perfect and the wife loved the present. She was away alot and we became really close, he was truly a friend. He knew, he understood. He welcomed our first child, our first house, our second child, our failed attempt at a friend (named him simba ) thats a whole different story, as my wife gave him away while I was at work... Never got a chance to say goodbye. He was a rescue kitten and mad at everyone in the world except me. He bit, scratched, hissed at everyone, but would snuggle with me all the time. The two cats hated each other, fought almost to the death, vet bills, crazy amounts but we loved them both.
I will never forget both of them, I suspect Simba is still alive but I have no idea.
We moved on and let our kids pick new cats but zazoo and simba will always be in our hearts.
Sorry you had to go through this too, rest happy you gave him the best life he could ever have had.