Welcome to the forum, even under such sad circumstances. I am sorry and very saddened to learn of your loss of your beloved Bentley, but I am glad for him (and you) that your paths crossed with his when they did, and that for a decade you two had many moments filled with love, affection, adoration and comfort.
So many of us here go through the "2nd guessing" and the "what if's?". It is evidently just part of what we must go through. They say: "When you choose to end the pain & suffering of a beloved pet, you then agree to take on their pain & suffering onto yourself. You absorb it through your grief. It is the bargain you make."
So this is what you are many of us here are having to endure. The pain & suffering that our pets would have felt if we had not shown them mercy. It is like transferred negative energy. We absorb it and must process it. Which takes time as we all know.
I too had to recently put to sleep my beloved boy. A cat named "Marmalade." He was my best friend, my son, my brother, my amigo, my compadre, my Samurai Cat! A fighter and a lover. My heart is shattered into a million pieces and I am endeavoring to put all of the pieces back together piece by piece.
Thank you for sharing some of Bentley and your story. And for the lovely photo that you shared. You can clearly see how much Bentley loved and adored you in it and how happy he made you!
There are so many good-hearted, kind, warm, loving, smart, witty and loving people who post here on this forum. Far longer that I have been here. But I have found it very comforting to visit and learn from them. I hope you will visit again here soon.
I send you my most sincere & warmest condolences,