Sounds like you need to warm the prey a little more. I often run my hands under cold water before feeding to lower my hand temperature but I'm just over cautious! Mine have never tried to get my hand, yet.
I also feed in my enclosure. I have a BP around the same size and she is on small weanling rats for comparison. If feeding multiples is working for you, great, but it may start getting expensive if he decides to just eat mice for his life :p