I am so very sorry for the loss of Fluffy!!!!! You both did the most loving unselfish thing you could possibly do for him. He will always know how much he was loved and still is loved and please keep that with you. It is hard because on top of loosing your beloved pet, you also have feelings of guilt and think for a few sec, oh did i do the right thing, that is what we went through with Ginger, but you absolutely did!!!
RIP sweeet Fluffy, you can go play with Mousse and Ginger, they love sweet kitties and I am sure they are missing there kitty.
God Bless both of you, I pray he continues to comfort you and help you along with your grieving and give you the peace you deserve.