After reading these posts about negative side weight and a lack of the "big backend", I can't help but wonder if the ball may be burning up (rolling out because the ball is not finding enough oil to skid down the lane and store energy before changing direction quickly and violently). When the ball does not make the move that you want it to does it roll straight into the pins?
What I mean is does the ball start to hook, make a change in direction, and then "straighten out" in that direction. If so, then the surface and pin position of the ball is a greater problem then negative side weight (which I apply to the theory that negative side weight has absolutely no noticable effect at all on ball reaction). If the ball is burning too much energy, then the correct step would be to either sand the ball to a finer grit (4000 or so), or preferably polish the ball. By polishing the ball, it will skid much further down the lane and store extremely more energy for the backend, thereby flipping much more violently.
I also notice that your 3 balls are all of significantly different weights (12, 14, and 16 lbs.). Before worrying so much about negative weight and weight holes on your NAP I would look at getting a more consistent weighted arsenal (which by the way, a weight hole on your NAP will most likely increase the tendency of the ball to roll out and tame the backend down farther due to the change in density distribution of the core which has a much larger effect on ball reaction than static weights).
Although having a slightly ligter spare ball may be ok for some people, having a 4 pound difference between two of your balls is a major problem. There is absolutely no way you can make that change consistently and expect to make a quality shot. To throw a lighter or heavier ball, you have to change something about your approach, which is garaunteed to mess with your timing in one way or another.
Just some suggestions,
good luck with the No Mercy.
-njv29