WP_Query args with repeater dates

alter_main_query_on_archives.php

<?php
add_action( 'pre_get_posts', 'custom_query_vars' );
function custom_query_vars( $query ) {
  if ( !is_admin() && $query->is_main_query()) {
    
    if ( is_post_type_archive('evenements')) {
      $today = date('Ymd');
      $sixMonthsPast = date('Ymd',strtotime('today -6 months'));
      $sixMonths = date('Ymd',strtotime('today +6 months'));

      $meta_query=array(
	  					'relation'		=> 'OR',
	  					array(
		 				'relation'		=> 'AND',
							array(
								'key'		=> 'dates_$_date_debut',
								'compare'	=> 'BETWEEN',
								'value'		=> array($sixMonthsPast,$sixMonths),
							),
							array(
								'key'		=> 'dates_$_date_fin',
								'compare'	=> 'BETWEEN',
								'value'		=> array($today,$sixMonths),
							)
							
						),
						
					);


      $query->set( 'posts_per_page', -1 );
      $query->set( 'meta_query', $meta_query );
      $query->set( 'orderby', 'meta_value_num' );
      $query->set( 'order', 'ASC' );
      
    }
    
  }
  return $query;
}

wp_query_events.php

<?php
$meta_query = array('relation' => 'OR');
	// construction de la requête car wpquery n'accèpte pas les tableaux
	foreach ($taxonomies as $key=>$v) {
		$tlist[]=$key;
	    $meta_query[] = array(
	        'key' => 'thematiques',
	        'value' => '"' . $key . '"',
	        'compare' => 'LIKE'
	    );
	}

	
	
	$args=array(
	  	 'post_type' => 'evenements'
	  	,'meta_key' =>  'dates_$_date_fin'
	  	,'order_by' => 'meta_value_num'
	  	,'order' => 'ASC'
	  	,'post__not_in' => array($id)
	  	,'posts_per_page'=> 3
	  	,'meta_query'	=> array(
	  					'relation' => 'AND',
	  						array(
								'key'		=> 'dates_$_date_fin',
								'compare'	=> '>=',
								'value'		=> $today,
							),  					
	  						$meta_query
	  			)
	);
	  $the_query = new WP_Query( $args );


/*
*
*
*
*/
function getEventsHome($atts){

	$today = date('Ymd');
	$atts = shortcode_atts(
		array(
			'num' => '10',
			'ordre' => 'DESC',
			'exclude' => null
		),
		$atts);
	// trop compliqué de prendre en considération l'heure de fin dans la requête 
	 $args=array(
	  	 'post_type' => 'evenements'
	  	,'order_by' => 'meta_value_num'
	  	,'order' => 'ASC'
	  	,'posts_per_page'=> $atts['num']
	  	,'meta_key' =>  'dates_$_date_fin'
	  	,'meta_value'=>$today
	  	,'meta_compare'=>'>='
							
							
	  	// )
	  	// ,'meta_query' => array(
				// 				'key'		=> 'dates_$_date_fin',
				// 				'compare'	=> '>=',
				// 				'value'		=> $today
							
	  	// )
	  );

	 if(isset($atts['exclude']) && !empty($atts['exclude'])){
	 	$args['post__not_in']=explode($atts['exclude']);
	 }

	 $the_query = new WP_Query( $args );