Snakes' skin is pretty tough, actually - I have never experienced injuries on any of mine from a rat or mouse kicking at them.
I feed all of mine live mice or small/small rats (which is the largest they will ever need) each week. There's not a scar or scratch on any of mine. I also do not ever interfere with the kill.
I doubt it - the "horrific" part for the snake might have been the other predator (you) interfering in his kill to take it from him (in his mind). But I seriously doubt he was horrified that the rat was kicking at him.but it most likely was a horrific experience for my snake
You'll find here at BP.net - we each keepers choice to feed whatever works best for them. For me, it's feeding live, for others, it's feeding f/t or pre-killed.
Since I've never fed f/t - I'll leave your question on how to convert to others more experienced in doing so.