[Antennas] questions on Windom

[RB]

I have a 136' (1/2 wave on 80m) Carolina Windom from Radio Works.  It's a good antenna, and works well for me.  

There is a transformer or balun at the feedpoint (14% off center).  Then, a 22' coax downdrop to a choke balun.  Coax on to the shack.  

What function does the choke balun play?  There's coax on both sides of it.  I thought unbalanced signal goes in one end of a choke balun, and balanced signal comes out.  Having coax on the balanced output side of the balun would seem to be counterproductive.  But, it works, and works well.  How/why?  

Does the off-center feed shift the current peak over by the amount of offset on some bands?  Is the current peak symmetrically centered on some bands?  What is the effect of off center feed?  

The antenna is rated for 160m use, too.  What do I have when on 160?  Is it sort of a 22' top loaded vertical?  It's a shortie, physically, for 160, if you consider only the horizontal part.  Likely very reactive---which is why power input rating on 160 is only 500 watts.