Sorry, but no, I have had to put down a few snakes. Occasionally hatchlings emerge with non-survivable deformities, and I had one snake that developed cancer.

Anyone who's breeding snakes will eventually have to face that same issue--not every egg will develop into a perfect baby. Whether it's due to a problem with the incubator, or simply a random mutation or developmental issue, every once in a while, a hatchling will come out kinked, with fused body parts, missing eyes, with jaw deformities, etc. Not everything goes perfectly in reproduction.

If there is a chance they can be saved, it's worth trying--if you know that there isn't, then it's best to put them down humanely so that they won't suffer.

As for how reptiles sense pain...one or two accidentally pinched tails later, I have to disagree with you completely. There's nothing wrong with their ability to sense pain. Adrenalin dulls pain, so of course an animal that is frightened and defensive is not going to waste time reacting to the pain beyond the initial flinch. Neither will any mammal, bird, or even a human. How many times have you heard of someone getting their foot bitten off by a shark, and swimming straight to shore? Do they spend time 'writhing in pain'? Heck no, there's no time for that in a survival situation.

Add to that the fact that reptiles (like many other animals) will instinctively seek to hide any signs of weakness, and of course you aren't going to see the kind of outward signs you were looking for. You won't see them in a dog, either.