Making my comments box smaller

Hi i am currently using the Pinboard theme and i absolutely love it. But i have a few problems that i cannot solve. First, how do i close the gap between the header image and the menu because even when i do not have any header widget, there is still a huge gap between the header image and the menu and i find that a little unpleasant. Second, i am having troubles making the comments area box smaller because the size of my comments box is half the size of the comments area which leaves me with too much excess space which again is unpleasant. Please help me, my website is http://www.thefashionistgrail.com