Solutions found for commented errors

I have been able to correct errors shown readed here doing the following:

Modifying the API call like this:

   //API URL to get product by ID.  Use https! 
   $requestURL = "https://" . $url . "/api/products/". $id . "&ws_key=" . $webservice_key;

Adding the API KEY to the image call:

   $image_id = sanitize_text_field((string)$parse_data->product->id_default_image); 
   $image_url = $url . "/api/images/products/" . $id . "/" .  $image_id . "&ws_key=" . $webservice_key; 

Plus if you want your prices shown TAX included, modify like this:

function ps_product_display_price($price)
{
   setlocale(LC_MONETARY, 'es_ES');
   return money_format('%.2n', $price*1.21);
}