Add this to your qa-theme.php file:
For 1.7+:
public function initialize() {
parent::initialize();
unset($this->content['navigation']['sub']['recent']);
}
For 1.6, you can use the same code but replace initialize with doctype.
In order to avoid getting to the most recent page by default, the easy way, would be to hack the core.
1. Locate this line.
2. Add the following code exactly in that line:
if (!in_array($sort, array('hot', 'votes', 'answers', 'views')))
$sort = 'X';
3. Edit the previous code so that X takes one of hot, votes, answers or views. Each of them represents one of the menu items. The value you replace X with will be the menu item that will be selected by default when clicking on the Questions menu item.