Your snake won't be injured if you monitor feedings like you're supposed to. Those horror pictures you see on the internet are only from irresponsible owners that keep rats in with their animals for very long periods of time. A lot of people on here have fed thousands of live prey and never had an issue. Your snake is your responsibility so you need to decide what you prefer. I have several snakes that eat both live and F/T and some that only eat live. I'm converting all over to live because of the amount of snakes I have and cost. It is cheaper for me to have my own rat colonies and feed live. The decision rests with you and what is easier to provide for your snakes.
Your prey are too small. I would definitely try larger. You should be using young mice or fuzzy/pup rats. Some of mine don't mess with really young rats/mice but will readily take an adult. I'm not sure if it's the movement or smell but definitely try larger prey items. Good luck!
Regards,
B