There's no way to scroll in fixed-layout, but you can remove the page flip effect and the fake binding in iBooks by adding some metadata in the .opf:
Code:
<meta property="rendition:spread">none</meta>
To remove the grey margins, you must specify a 4:3 proportion for your page in the XHTML (for each page – viewport meta tag) and in the CSS (body tag/background images). You must also lock the orientation (landscape or portrait).
Code:
<meta property="rendition:orientation">landscape</meta>