Chin length would probably typically stay behind the ears. 

As for the part, that is a personal preference.  My part (when I have one) is slightly off center due to a spot at my hairline where my hair does not grow.  Most people don't even realize it.  Many people will use a side part in order to give more lift to the hair.

Good luck in growing out your bangs.... I think they are the toughest part of growing out hair.