Is it possible to measure the values for endstates precisely?

For the end states, it is advisable to approach the correct values slowly. Unfortunately, it would be hard to find an absolute, correct value. It is always a trade-off between stability and accuracy:

• For example, if you set the minimum contact force precisely, the robot becomes unstable to vibrations (program stops).
• If you don't set a minimum force at all, the arm will push the target in front of it (accuracy will be missed).

The correct values depend on the task itself, the robot design, disturbing influences (vibrations) and others.

As a rule, it is sufficient to try it out until the accuracy is right.

See this too: End State Parameters - How to Stop a Skill