This is so sad...yet it is also such a valiant experience, in every respect.
Stuart had the odds against him from the beginning, and the odds were that he would end up far worse than what they were with you. He got the best, and you should feel proud of that, not sad, not betrayed or angry, not at yourself or Stuart.
The photo with his eyes in it says a lot, really. I don't know that he was ever allowed to grow, to mature, and to know the confidence of love, until he came to you. Some of the damage was obviously too deeply ingrained to fully heal.
I'm sorry you had to get hurt so badly, but that is just proof of how far you were willing to go for him, out of love. No shame in that.
Thank you for sharing so eloquently. would that all dog owners would put even 1/8th that effort into their puppies!
Liz