Adding Search & Filter to custom WP_Query?

I’m using Search & Filter Pro, and want to add it to my currently setup WP_Query:

if( get_sub_field('type_of_post') == 'age' ) {
  $post_type = 'courses';
  $taxonomy = 'ages';
  $term = get_sub_field( "age_category_posts" );
  $orderby = 'meta_value_num';
  $order = 'ASC';
  $meta_key = 'courses_order';
  $the_tax_query = $the_query;
  $post_per_page = '100000000';
} else { }

$the_query = new WP_Query( array(
  'posts_per_page'=> $post_per_page,
  'post_type'=> $post_type,
  'orderby' => $orderby,
  'order' => $order,
  'paged' => $paged,
  'meta_key' => $meta_key,
  ‘search_filter_id’ => '1835',
  'tax_query' => array(
     array(
       'taxonomy' => $taxonomy,
        'field' => 'term_id',
        'terms' => $term,
    )
    ),
    'paged' => get_query_var('paged') ? get_query_var('paged') : 1) 
    ); 

I’ve then added the following shortcode:

<?php echo do_shortcode( '[searchandfilter id="1835"]' ); ?>

The form appears, ajax is turned on, but it just doesn’t seem to work.

Am I better of custom coding a search filtering system like this, or using this plugin? I want it to work as follows:
On a page for 15 year olds, courses show as below in WP Query by selecting ’15’ in ‘ages’ taxonomy within ACF. I then want to be able to filter through the courses assigned the taxonomy 15 based on another taxonomy assigned to that custom post type ‘subject’.

Thanks,
Meg