to remove all the content from the about us page, open it in Dreamweaver and go to Modify -> Tempales -> Detach From template.
you wont be able to remove the side menu form the contact us page with out editing the theme and effecting all pages.
to remove the links from the menu, you need to edit the CSSMenuWriter/cssmw/menu.php page.
try doing the same for the home page, detach it from the template.
Power Store is designed to work the way it does out of the box. You ask: "Will that cause any problems" any time you edit a pre designed application it can cause problems. I cant really say if it will or not, but it may.