tb_blog main area left padding
That theme is using a grid, looks like a base of 24. It's not the padding that's causing the blog to not display in the full page, but the grid (IE, the grid widths). 

If your uncomfortable with updating the css of this theme, you may want to switch to a theme that's not grid based. Though it's not full page, business or something like it might be more suited to what you want to do.