This is such an unfortunate incident to have happened. You have been given some good sound advice. I would definitely put that poor animal out of it's misery. Imagine having a wound like that yourself. You would be in a lot of pain and would be miserable. That poor baby has very little chance of survival and that is really sad. Animals come into our lives and we are obligated to take care of them and provide for their needs. In this case, you have a very difficult decision to make. I had a cat that was very sick and last year I had to make the choice to put him down or let him suffer. I did the obvious thing and ended his suffering. Did it hurt for a while, sure it did. I was not going to be selfish and keep him alive for my own liking. I know you will make the right decision because it is obvious you really care about this animal. Please please please do not allow this snake suffer any longer then is absolutely necessary.