Select the option , Without stub.
Then the rest is automatic.
In older versions of NX, one set the "stub length" to 0, but newer versions has this option "without stub".
1.) How to make off-set leaders that are not locked to a certain line on part ?
If you're using the Autoballoon functionality, you cannot have the system terminate the leaders on faces of components - it will only use the edge curves of the components.
ER 1815564 - Cannot define faces as terminating object while creating auto ballons.
Having selected Autoballoon, right click a leader and choose Edit. Pick the location on the face of the component where you want to terminate the leader and then close the Balloon dialog. The annotation in the balloon will remain associative to the Parts List.