Get 3D Motion path Data

hi, everybody...

I converted a regular motion path to 3D motion path by doing this:

1.) Paste a spiral motion path from illustrator to the position parameter of a 3D Null 1
2.) Create a 3D Null 2 and parent Null 1 to it.
3.) Rotate Null 2: X-axis 90 degrees.
4.) Set auto-orient to Orient along path on Null 1 (optional)
5.) Parent the object you want animated to Null 1

Questions

1.] Everything works fine,BUT how do I access the new 3D positional values of the motion path (Null 1 + Null 2).

2.] The arrow periodically jerk rotates along the path, how can I get the motion to be fluid without gimbal jerky rotation.

here's the project sample:

http://www.simulationbox.com/outgoing/arrowX.aep

Thanks
Sincerely,
Charlie