Also holding a mouse or rat by the tail during feeding live is a bad idea as the rat is on the defensive. If you are going to continue feeding live, just put the rat in there nice and calm. That was he isn't really ready when the snake strikes and by then its too late anyways. I personally just pre killed or F/T to all my gals. My BP started on live rat fuzzies since they couldn't hurt her. Then once she was up to weanlings, I would just pre kill them and she took them fine. Now I just do F/T for everyone as I'm lazy and I definitely don't want to try and kill weaned rabbits for my big boa.
And I know you feel about the sizing. I have a reptile shop by me who stocked all the sizes of rats and mice down to newborns. Sounds like you need something like a weanling rat or maybe a large crawler. Check and see if you have any reptile shops close to you. I know I have to drive about 40 mins each way every couple weeks to get my big boa her F/T weaned rabbits but its the same place that has all the live stuff too so I'm used it by now lol.