This is so heartbreaking to read. Merlin looked like Cora, my son's best friend's cat who often spends time at our house, and now she's with us these days. She's a young kitty with a lot of attitude.
I don't know what to tell you that can comfort you. But beyond the sadness of the last moments, it is clear you had a great and faithful friend in Merlin who will always live in your heart.
It's really amazing how cats behave sometimes. You mention attitude. Merlin was like that: Confident, strong and a good hunter. He had, presence. But when Cleo came along ten years ago...He was a big softie. He loved her straight away and she became his shadow. He looked after her so well. Cats are such interesting little things.
Merlin was such an amazing little fellow to have in my life and I'll remember him always.
Now I'm off to give Cleo a cuddle.