Theme Customizer not displaying saved values in wp_head

<?php
  /**
   * mytheme Customizer functionality
   *
   * @package WordPress
   * @subpackage mytheme
   * @since mytheme 1.0
   */
  class mytheme_Customize {
   /**
   * Add postMessage support for site title and description for the Customizer.
   *
   * @since mytheme 1.0
   *
   * @param WP_Customize_Manager $wp_customize Customizer object.
   */
public static function register ( $wp_customize ) {

// Sidebar Layout

$wp_customize->add_section( 'mythem_sidebar_layout_section' , array(
    'title'         => __( 'Sidebar Layout', 'mythem' ),
    'capability'  => 'edit_theme_options', //Capability needed to tweak
) );

$wp_customize->add_setting( 'mythem_cus[sidebar_position]', array(
    'capability' => 'edit_theme_options', //Optional. Special permissions for accessing this setting.
    'sanitize_callback' => 'mythem_validate_sidebar_position',
) );

$wp_customize->add_control( new WP_Customize_Control( $wp_customize, 'mythem_cus[sidebar_position]', array(
    'label'         =>   esc_html__( 'Sidebar Position', 'mythem' ),
    'type'          =>  'radio',
    'choices'       =>  array(
      'left'        => esc_html__( 'left', 'mythem' ),
      'right'       => esc_html__( 'right', 'mythem' ),
      'no-sidebar'  => esc_html__( 'no-sidebar', 'mythem' )
      ),
    'section'       =>  'mythem_sidebar_layout_section',
    'settings'      =>  'mythem_cus[sidebar_position]',

) ) );

}
  }

  function mytheme_mod( $key , $default = false ){
    $mytheme_cus = get_theme_mod('mytheme_cus');
    return isset($mytheme_cus[$key]) && $mytheme_cus[$key] ? $mytheme_cus[$key] : $default;
  }

  function mytheme_sidebar_layout() {

    $mytheme_sidebar_position = mytheme_mod('sidebar_position');

    if($mytheme_sidebar_position === 'left') {
      echo "<style>";
      echo ".site-content .widget-area {float: $mytheme_sidebar_position; overflow: hidden;  width: 30%;}";
      echo ".content-area {float: right; margin: 0 0 0 -30%; width: 100%; }";
      echo ".site-main {margin: 0 0 0 32%;}";
      echo "</style>";
    }

    if($mytheme_sidebar_position === 'right') {
      echo "<style>";
      echo ".site-content .widget-area {float: $mytheme_sidebar_position; overflow: hidden; width: 30%;}";
      echo ".content-area {float: left; margin: 0 -30% 0 0; width: 100%; }";
      echo ".site-main {margin: 0 30% 0 0;}";
      echo "</style>";
    }

    if($mytheme_sidebar_position === 'no-sidebar') {
      echo "<style>";
      echo ".site-content {width: 100%; float: none;}";
      echo ".site-content .widget-area {display: none;}";
      echo ".site-main {margin: 0;}";
      echo "</style>";
    }

  }

  add_action( 'wp_head', 'mytheme_sidebar_layout' );