I would also aim low, anticipating that he would tryand jump the string.
But he's standing in tall grass which would screw your arrow flight up. I think this is a question that really has no right answer. Its all about your ablility,equipment, confidence, etc.... I think I would have taken the shot as thats a once in a lifetime deer and I think i'd have the means to make a good shot. I hope you get another look and I don't disagree with your decision at all.