Hi, the code in the FAQ's was not yet adapted to the plugin version 1.5+
Moving the snippet to after the wp_footer() call in footer.php will indeed work. Another method can be to use this code in a text widget:
<script type="text/javascript">
var pixelRatio = window.devicePixelRatio || 1;
if(window.innerWidth/pixelRatio < 641 ) {
easy_fancybox_handler = null;
};
</script>