Loyal loving pets are one of God's greatest gifts, but He takes them back from us very soon. We are taught lessons to cherish their fleeting short lives.
I'm sorry for your loss. It never gets easy. I've had the highs of pets, and the lows, many times. They give some of the greatest joys, but also greatest sorrows when we lose them. Your caring for him all these years, humane treatment at the end, and memory, is noble.
I don't need to post a photo of our 20 year + 10 day old cat, Marcus as he's Jack's twin.
Marcus had a littermate brother who died ~4 years ago.
They were rescue cats which had been returned. We didn't rename them as they were "answering" just fine.
Condolences extended from The Garden State.
AND, if anyone wants to have a great night out with outstanding food and is near The Township of Washington, NJ and wants to support a great animal (mostly cats) shelter, consider attending.
I feel bad for you having been through the same with with other cats. After our last one died my wife said no more. But one day while visiting a local farmer one of his many barn cats came to me instead of the food being put out and latched on to me. The next day she was home with us. That was 6 years ago and now she is more than just part of the family, she rules the roost.