Add Custom Values to Permalinks Through Custom Fields and Posts

I fixed this issue by adding a rewrite rule to my functions.php file at the top:

function melon_rewrites($rules) {
        $new_rules = array(
            'parties/([^/]*)/([^/]*)$' => 'index.php?melon-parties=$matches[2]'
        );
        $rules = $new_rules + $rules;
        return $rules;
    }
    add_filter('rewrite_rules_array', 'melon_rewrites');

I then changed my cpt to allow a query_var:

function register_custom_post_types() {
    $args = array(
        'labels' => array(
            'name' => __( 'Parties' ),
            'singular_name' => __( 'Party' )
        ),
        'menu_position' => 50,
        'public' => true,
        'has_archive' => 'true',
        'hierarchical' => true,
        'taxonomies' => array('party-tags'),
        'capability_type' => 'post',
        'query_var' => true,
        'rewrite' => false,
        'supports' => array('title', 'editor', 'thumbnail', 'revisions', 'page-attributes')
    );

    register_post_type('melon-parties', $args);

    $args = array(
        'labels' => array(
            'name' => __( 'Type of Parties' ),
            'singular_name' => __( 'Type of Party' )
        ),
        'menu_position' => 50,
        'public' => true,
        'has_archive' => 'true',
        'hierarchical' => true,
        'show_ui' => true,
        'publicly_queryable' => true,
        'capability_type' => 'page',
        'query_var' => true,
        'supports' => array('title', 'thumbnail', 'revisions', 'page-attributes'),
        'rewrite' => false
    );

    register_post_type('party-categories', $args);

    $args = array(
        'labels' => array(
            'name' => __( 'Home Slider' ),
            'singular_name' => __( 'Home Slide' )
        ),
        'menu_position' => 50,
        'public' => false,
        'show_ui' => true,
        'hierarchical' => false,
        'publicly_queryable' => true,
        'capability_type' => 'post',
        'supports' => array('title', 'editor', 'thumbnail', 'revisions', 'page-attributes')
    );

    register_post_type('melon-home-slider', $args);

    $args = array(
        'labels' => array(
            'name' => __( 'Case Studies' ),
            'singular_name' => __( 'Case Study' )
        ),
        'menu_position' => 50,
        'public' => true,
        'hierarchical' => false,
        'publicly_queryable' => true,
        'capability_type' => 'post',
        'rewrite' => array('with_front' => false, 'slug' => 'case-studies'),
        'supports' => array('title', 'editor', 'thumbnail', 'revisions', 'page-attributes')
    );

    register_post_type('melon-case-studies', $args);
}
add_action( 'init', 'register_custom_post_types' );

I also had to make a couple changes to my rewrite rules as i wasnt actually pointing to my cpt:

add_action('init', 'tdd_add_rewrite_rules');

    function tdd_add_rewrite_rules() {

    // Register custom rewrite rules
        add_rewrite_tag('%melon-parties%', '([^/]+)');
        add_rewrite_tag('%party-categories%', '([^/]+)');

        add_permastruct('melon-parties', 'parties/%party-categories%/%melon-parties%', false);
    }

    add_filter('post_type_link', 'tdd_permalinks', 10, 3);

        function tdd_permalinks($permalink, $post, $leavename) {

        $no_data="no-category";

        $post_id = $post->ID;

        if($post->post_type != 'melon-parties' || empty($permalink) || in_array($post->post_status, array('draft', 'pending', 'auto-draft')))

        return $permalink;

        $var1 = get_post_meta($post_id, 'cmb-event_category', true);

        $var1 = get_the_title($var1);

        $var1 = sanitize_title($var1);

        if(!$var1) { $var1 = $no_data; }

        $permalink = str_replace('%party-categories%', $var1, $permalink);

        return $permalink;

    }

    add_action('init', 'partyCategoryRewriteRules');

    function partyCategoryRewriteRules() {

    // Register custom rewrite rules

        global $wp_rewrite;
        $wp_rewrite->add_rewrite_tag('%party-categories%', '([^/]+)', 'party-categories=");

        $wp_rewrite->add_permastruct("party-categories', '/parties/%party-categories%', false);
    }

    add_filter('post_type_link', 'partyCategoryPermalinks', 10, 3);

        function partyCategoryPermalinks($permalink, $post, $leavename) {

        $no_data="no-category";

        $post_id = $post->ID;

        if($post->post_type != 'party-categories' || empty($permalink) || in_array($post->post_status, array('draft', 'pending', 'auto-draft')))

        return $permalink;

        $var1 = $post->post_name;

        $var1 = sanitize_title($var1);

        if(!$var1) { $var1 = $no_data; }

        $permalink = str_replace('%party-categories%', $var1, $permalink);

        return $permalink;

    }

Now my url structure is correct