I think you're overreacting a bit, that mouse was doomed from the get go. These guys are killing machines and I see nothing but the efficient handling of an overly large, defensive mouse. Some 20 years ago feeding once a month was the norm for me and my snakes all got rather huge(in proportion to their bodies), live meals. In hundreds of feedings I never got more than a superficial bite to one of my snakes.
***disclaimer***
I now feed every 4-10 days(depending on animal) and more appropriately sized meals. I just wanted to share my past experiences and observations.