For the sake of pointing out the bleedin' obvious, (and apologies if you've already tried) - wharra 'bout trying to flick the line casting style?
My pole (made of spars from Morning Cloud) is taller than yours and it worked well for me. It took ages to free the end, with gentle flicks the line came slowly down.
Next time put a weight (old tyre balance weights?) at the top end and it'll come down easier.
(Mark you the suggestion of a roach pole - which methinks was an idle suggestion for a new flag pole - adapted by you to lasso the free end looks like a cracking idea, but it might take two people to manage it)