^The link just above had some great code, taking into account C2 physics.
I put something together in a hurry in an attempt to help. It may just confuse you more and be needlessly complicated, but, drag the red dot, then release:
http://arrall.com/c2/motionmarkers
Something like that?
I looked at your capx. Nice what you've done with the bow, string, and arrow. The arrow travels rather fast with minimal drawing of the bow.