I agree with Jeff. The shorter string should make no difference. I suspect that you are somehow tipping your hand so that you draw more with the ring finger. AFTER your finger feels OK, try working on your grip/release and see if you can get a more even pull with all fingers. As for finger pinch with a short bow (mine is 54"), I just pull with the ring finger and the middle finger (two below). The pointer finger does just that, it sits next to the arrow, touching the nock, and pointing at the target.