I'd try 42 psi fuel, 950-1000 psi nitrous, and 12 deg. initial... and you already run a colder plug, right? See what that does for you... you might just find that 20hp you're looking for...
The low bottle psi coupled with the high fuel psi could explain the rich condition that would cause a loss in power... what is your fuel psi when spraying? Isn't it supposed to be around 80 psi on a dry kit?
Have you consulted with the guy that you linked to from the corral? If you do another dyno session, try the 75hp jets and see what happens... good luck
