MY GRIP WAS WRONG!
All suggestions were appreciated. While my hands are not gigantic, I am a big guy. The Shield is a fairly small pistol - I found that I was not using my left hand properly (non-trigger finger) and was dominating my grip with my right hand. When I worked on using more left-hand pressure, I found this eased up the tension on my right hand (which was, undoubtedly, causing my to shoot low and left).
The shots are not perfect yet, but I'm on my way! Thanks again for all the great advice.