Watching him lie on my chest, declining rapidly, is an agony I can't get out of my head and I would not wish on anyone else. I will carry those few final hours with him with me until my last day here. I understand the rationale behind giving him pain meds and seeing what will happen. It's probably what I would have done too. As long as he's not in pain and acts fine, it should be ok. Until it isn't. And when it isn't it will come in a big hurry.
I couldn't have said it better. I had a similar experience with one of my beloved boys. We had just come home from the Vet when he started declining. I was so happy that he was able to lie in my arms and feel my love as he crossed the Rainbow Bridge. As painful as it was for me, I was somewhat comforted by the fact that he was able to pass in his safe space....lying on my chest. Try to separate what is best for Amigo from what you wish for him. It's not always easy.