Recursive call for cron job

Question

I have a three PHP script, from which two are running as a separate cron job each day in server. First script(get_products.php), make curl call to external server to get all products data and stored that data in database. Note that there are around 10000 products and increasing each day.

In Second script(find_related.php), selects products from database stored by first script, perform some operations and store operational data in another database. Each product have 10 rows so in this database there is around 100000 rows. This script is running as cron. Sometimes the script is not executed fully and that's why, the actual and expecting results are not stored in database. I included this line of code in script: ini_set('max_execution_time', '3600');
But it not works.

Here is the process done in this script: Normally task is to find 10 related products based on tags. I have around 10300 products stored in my DB. Each time query take one product and their tags and try to randomly find one product tagged with same tag as main product and store the related product data into another DB for third script. Only one product per tag is allowed. If it will not find total of 10 related products then randomly gets products from another DB named bestseller_products. Here is my code:

    $get_all_products = mysql_query('SELECT * FROM store_products');
    while($get_products_sql_res = mysql_fetch_array($get_all_products)){
    $related_products = array();
    $tags = explode(",",$get_products_sql_res['product_tags']);
    $product_id = $get_products_sql_res['product_id'];
    $product_handle = $get_products_sql_res['product_handle'];
    $get_products_sql = mysql_query('SELECT * FROM related_products WHERE product_handle="'.$product_handle.'"');
    if (mysql_num_rows($get_products_sql)==0)
    {
        $count = 0;
        foreach($tags as $t){
            $get_related_products_sql = mysql_query("SELECT product_handle, product_title, product_image FROM store_products WHERE product_tags like '%".$t."%' AND product_id != '".$product_id."' ORDER BY RAND()");
            if(!$get_related_products_sql){
                continue;   
            }
            while($get_related_products = mysql_fetch_array($get_related_products_sql) ){
                $related_product_title = mysql_real_escape_string($get_related_products['product_title']);
                $found = false;
                foreach($related_products as $r){
                    if($r['handle'] == $get_related_products['product_handle']){
                        $found = true;
                        break;  
                    }   
                }
                if($found == false){
                    $related_products[$count]['handle'] = $get_related_products['product_handle'];
                    mysql_query("INSERT INTO related_products (product_handle, product_id, related_product_title, related_product_image, related_product_handle) VALUES ('$product_handle','$product_id','$related_product_title', '$get_related_products[2]', '$get_related_products[0]')");
                    $count = $count + 1;    
                    break;  
                }
            }
        }
        if($count < 10){

            $bestseller_products = mysql_query("SELECT product_handle, product_title, product_image FROM bestseller_products WHERE product_id != '".$product_id."' ORDER BY RAND() LIMIT 10");
            while($bestseller_products_sql_res = mysql_fetch_array($bestseller_products)){
                if($count < 10){
                $found = false;
                $related_product_title = mysql_real_escape_string($bestseller_products_sql_res['product_title']);
                $related_product_handle = $bestseller_products_sql_res['product_handle'];
                foreach($related_products as $r){
                    if($r['handle'] == $related_product_handle){
                        $found = true;
                        break;  
                    }   
                }
                if($found == false){
                    $related_product_image = $bestseller_products_sql_res['product_image'];
                    mysql_query("INSERT INTO related_products (product_handle, product_id, related_product_title, related_product_image, related_product_handle) VALUES ('$product_handle','$product_id','$related_product_title', '$related_product_image', '$related_product_handle')");  
                    $count = $count + 1;
                }
                }
            }
        }
    }
}

Third script(create_metafields.php), created metafields in external server using data created by second script. And same problem arises as in second script.

So i want to execute the second script into parts. I mean, not to process all 10000 products in one call but want to run unto parts(1-500,501-1000,1001-1500,..) like it. But dont want to create separate cron jobs. Please suggest if someone has solution. I really need to figure it out.

Thanks in advance!