Instead of using "Menu" as the mobile text menu, use font awesome "Bars "
<nav id="site-navigation" class="main-navigation" role="navigation">
<button class="menu-toggle"><?php _e( '<i class="fa fa-bars"></i>', 'custom' ); ?></button>
<?php wp_nav_menu( array( 'theme_location' => 'primary' ) ); ?>
</nav><!-- END #site-navigation -->
@media screen and (max-width: 719px)
.menu-toggle {
padding: 0 2em;
}