You'll need to increase the number for per_page in the shortcode to increase the number of products shown. Either that or try changing your permalink settings in Settings>Permalinks to default and see if that helps. If it does, then you may need to go through some wordpress troubleshooting steps to fix your permalinks: http://codex.wordpress.org/Using_Permalinks#Fixing_Permalink_Problems
To remove the default widgets, just add empty text widgets to each of the footer areas in the Appearance>Widgets section of wordpress.
If you have any other questions just make a new topic and we'll do our best to help :)