rcmck

That should work if you add it to a php template file. If you are adding it into a post/page’s content in wp-admin you’ll need some type of php execution plugin to handle that. Such as:
http://ww.wp.xz.cn/extend/plugins/exec-php/

The first one is the one on the messed up page.

/wp-login doesn’t exist.

You have to go to /wp-login.php or /wp-admin

The problem is most definitely in` your styles. And here’s where:
line 242

.custom-layouts.singular #content {
    margin: 0 7.6%;
    position: relative;
    width: auto;
}

Is overriding your width and margin settings that you have for the #content element on your homepage, line 152:

.three-column #content {
    margin: 0 34% 0 26.4%;
    width: 40.4%;
}

Simple class to add sortable user meta columns to wp-admin/users.php table. (You can also add wp_users columns).

/**
 * Add columns to the wp-admin user's table
 *
 * @param array $args Associative array where key is wp_usermeta meta_keys or wp_users column names and the value is the display name
 * @return none;
 */
if(!function_exists(load_sortable_user_meta_columns)){
	add_action('admin_init', 'load_sortable_user_meta_columns');
	function load_sortable_user_meta_columns(){
		//THIS IS WHERE YOU ADD THE meta_key => display-title values
		$args = array('nickname'=>'Nickname', 'user_registered'=>'Date Registered');
		new sortable_user_meta_columns($args);
	}
}
if(!class_exists(sortable_user_meta_columns)):
class sortable_user_meta_columns{
	var $defaults = array('nicename', 'email', 'url', 'registered','user_nicename', 'user_email', 'user_url', 'user_registered','display_name','name','post_count','ID','id','user_login');
	function __construct($args){
		$this->args = $args;
		add_action('pre_user_query', array(&$this, 'query'));
		add_action('manage_users_custom_column',  array(&$this, 'content'), 10, 3);
		add_filter('manage_users_columns', array(&$this, 'columns'));
		add_filter( 'manage_users_sortable_columns', array(&$this, 'sortable') );
	}
	function query($query){
		$vars = $query->query_vars;
		if(in_array($vars['orderby'], $this->defaults)) return;
		$title = $this->args[$vars['orderby']];
		if(!empty($title)){
			   $query->query_from .= " LEFT JOIN wp_usermeta m ON (wp_users.ID = m.user_id  AND m.meta_key = '$vars[orderby]')";
			   $query->query_orderby = "ORDER BY m.meta_value ".$vars['order'];
		}
	}
	function columns($columns) {
		foreach($this->args as $key=>$value){
			$columns[$key] = $value;
		}
		return $columns;
	}
	function sortable($columns){
		foreach($this->args as $key=>$value){
			$columns[$key] = $key;
		}
		return $columns;
	}
	function content($value, $column_name, $user_id) {
		$user = get_userdata( $user_id );
		return $user->$column_name;
	}
}
endif;