As I read this tears started. I understand how you feel. I had to do this a couple of years ago with the best dog I ever had the privilege of loving. We were kindred spirits and I loved her so. She got ill quite suddenly and there was nothing we could do for her. The only thing I can say is that she didn't suffer long. She only lasted 5 days until I had to call the vet and she was put down in her home in my arms. It was weird tho as we had two cats. One not friendly at all with anyone outside our immediate family who came over and sat with the vet and accepted pats without a fuss and even stood on his lap for a moment and then proceeded to go thru his medical bag. But both cats sat there while he did his business and after they both walked away. In the days after, they would lay in the spot where she passed. I had decided to move their food bowls back onto the floor in the kitchen since Annie wouldn't eat their food on them anymore but they didn't appreciate it and wouldn't eat there at Annie's place so I had to move it back on top of my filing cabinet.
Anyway, I'm sorry I rambled on and hijacked your thread. I just want to say that I'm sorry for about your little Rodney. But you did the right thing for him and I'm sure he knew that.