How do I format custom columns in the list view for custom post types?

I have the following code, which works approximately as expected:

add_filter('manage_knowledgebase_posts_columns', 'wpkb_columns' );

    function wpkb_columns( $defaults ) {
    	$defaults['upvotes'] = __('<strong>U</strong>');
    	$defaults['downvotes'] = __('<strong>D</strong>');
    	return $defaults;
    }

    add_action( 'manage_knowledgebase_posts_custom_column', 'wpkb_custom_columns' );

    function wpkb_custom_columns( $column ){
    	global $post;

    	switch ( $column )
    	{
    		case 'upvotes':
    			$upvotes = count( get_post_meta( $post->ID, 'upvote' ) );
    			echo $upvotes;
    			break;
    		case 'downvotes':
    			$downvotes = count( get_post_meta( $post->ID, 'downvote' ) );
    			echo $downvotes;
    			break;
    	}
    }

The edit.php page shows the upvotes/downvotes columns as fat, unsortable columns on the right hand side. I’d like to do the following:

• Specify column width
• Specify column order
• Make columns sortable

What’s the best way to do this?

[Cross posted from stack overflow]