Update: He's Gone
He passed away peacefully at 4PM EST on Sunday Feb 11th. He was acting completely out of sorts and was clearly in pain so I decided to call Lap of Love to evaluate and then proceed with the euthanasia. My vet called me today and suggested that he might have had pancreatic cancer, and that if he was in that much pain, I made the right choice. I was there until the end, it was very calm, he pretty much just went to sleep. I've been crying nonstop. I know it's not true, but it feels like I killed him. But I think I did the right thing for him, for him, always for him.
I'm staying with family for the time being. It's going to be so hard to go back home and clear out his things, but it'll be better when it's over. I'm going to donate all of the GI Low Fat canned food to a local shelter and give away as much as possible. I may keep a couple of things just for when I'm ready to welcome a new dog home again, but it might be a while.
After it all, I feel simultaneously heavier and lighter. I'm not sure if I'm the same person after yesterday. It is an extremely odd feeling.
Thank you for all your support in guiding me to the right decision for his well-being.