You can give another mouse without worries, but remember as well that BP's are binge feeders. It's their instinct to eat as much as possible when available...like college kids around free beer. It won't hurt, but may not be necessary (I guess that's where the college kid analogy ends!).
Something as thick as the snake is at its widest point, once per week, is a good rule of thumb.
For the weight percentages per week, I have heard as low as 10% and as high as 25% and everything in between!
JonV