Sorry free - he looks just like my crooked cat, Sylvie. She had a lesion on a nerve to her brain when she was about 2 which caused some bad issues too. Luckily she survived but to this day still walks with a head tilt.
So sorry to hear the sad news. I know that you know you did what was right, and he had a wonderful life and peaceful passing -- but I also know it's still hard. Hugs and prayers coming your way. Topaz was a beautiful kitty, very lucky to have had you and your love.