Predators backplot rotates the tool and not the stock.. I dont think there is a way to change that.. Also, I dont think there is a way to query an existing UCS's coords and rotation values?? Short of you could just draw some geometry then switch back to a top view and measure it..
With your model, why are you having trouble using pick 3 points?? Maybe extracting the edges you want to pick to make it easier? Or if you know those values, just use the coords placment, then modify it and rotate it.. (Sounds like thats what your doing?)