I cannot tell you how early to arrive, but I will say that if you're going during Party Season, the park is very crowded on non party nights. Buy the time the CTM show is scheduled to start, it is shoulder to shoulder, so if having a specific spot is important to you allow at least an hour, if not more. I have been in the park on Saturday nights for both CHristmas and Halloween seasons and by early afternoon it is extremely crowded. Everyone wants the evening entertainment and they are all trying to so the same as you are....see WIshes froma. Special vantage point.
As far as the crowd calendars go, I stopped relying on them other than to to assist in planning best park days. The numbers creep up as Disney offeres discounts that fill their rooms.
