Regarding body.... you said you wanted this at 100%, so don't give it a min or max width. Set the width to 100%.
Regarding .body_wrapper:
HTML Code:
margin-left: 50%;
margin-right: 50%;
What are you hoping to accomplish by making each margin 50% wide? That kinda uses up the whole page. (50% left and 50% right leaves nothing in the middle if added up.) If you have a fixed width, then the left and right margin need to be set to auto, not any number.