I am so sorry for the loss of Simon. I can't even imagine. Sending many hugs to you right now. While it is probably of little comfort (if any), at least you have answers now.
My heart goes out to you, I know the pain of losing someone that filled up your heart and your home with their presence. Now both are empty and it takes a long time for a broken heart to heal. I do know taht your sweet Simon would never want you to be so sad when you are remembering him, he would want you to celebrate what you two had shared, and one day pass on that legacy of love to another. I pray that your precious memories of a happier time will comfort you in the years ahead, and that one day you will find happiness again to fill your life with joy. Please know I will keep you both in my thoughts and prayers, take care of yourself......RIP beautiful Simon, the world lost a beautiful cat, but the heavens gained a precious angel!