XSI and Hahnel Remote question

I am trying to use a Hahnel shutter release cable, pictured here http://www.amazon.com …e-Extension/dp/B0019Y199​C

I am a dslr newbie (Christmas present), and would appreciate help with a few questions. The following questions and comments all refer to the use of the Hahnel remote shutter release cable with the Rebel XSI.

1. I understand that a 1/2 press of the button on this shutter release will auto-focus. I can see evidence of this in the focus point (I have it set to center) in P mode, but in Auto mode, the picture comes out "ok" but I can't use the shutter release cable and determine which focus point is active. Shouldn't I be able to?
   
2. Using a tripod and the Hahnel shutter release with my XSI, should I be able to depress the Hahnel 1/2 way to focus, and then reframe and continue the shot? (Am I expressing my question?)

What is happening is that I can't seem to hold a 1/2 press on the Hahnel. In P mode, it auto-focuses and takes the picture in one quick swoop. In Auto mode, I'm not even sure which focus point gets used! I've practiced and practiced and practiced with a light touch, but the results are the same.

Thank you in advance for help, advice, and/or a source to read.

Edit - 2 hours later:
Question 3 - Or can someone tell me, how do wired shutter releases normally work? Would you "expect" that I could hold the auto focus (1/2 press) before the shot is captured? Would you expect that I could identify in Auto mode, which focus points are being used with the cable shutter release? Which wired shutter releases do you use to accomplish this?