Robot type?
Software Version?
Hardware version?
Mechanical position of robot?
You provided a kartesian position, but no corresponding user tool and user frame data.
At the moment I can't help on the exact problem, just asking for the data someone needs to help.
I think you will have the problem at p = 90° (in this case w = 0°)
The W,P, and R angles are actually Euler angles. They are not always going to be an intuitive value depending on the orientation of the robot.
Can you tell us your what you are trying to accomplish by reading the angles? Maybe there is a different solution.
Why do you need to compensate for tool weight? Can you describe the application?
A picture might help to understand. If the robot is holding all of the load of your tool then why would orientation change the pressure applied?
A mechanical solution would be a much better way to go. There are also software options to apply a constant force with a force sensor.
Ok force sensor but price is a problem. 
And I'm not sure how sensitive the whole system is.
It is mechanical-pneumatic on rails.
when it is in a horizontal position, the weight of the tool does not exist, in all other orientations its weight exists and is different in different orientations.
the tool weighs about 3.5 kg and the pressure I want to apply is much smaller, 100g to 1000g.
