Veph, I'm so sorry to hear about your baby. I'll just echo what others have said before and say that I don't know that there's much more you could have done. You had taken the steps to get him taken care of, there's no way you could have known it would happen the way it did. I suppose when you think about it, it's a good thing you were awake to be with him in his final moments. One of my rats, Whipple, from a few years ago, died in my hands. She was old, and it took almost an hour, but I never left her and I held her the whole time, and I wouldn't have had it any other way. At least the last thing he saw while he was in this world was your face, the face he knew and loved his whole life.
Hugs and love your way, my dear.