in the server behaviors panel, double click the insert record behavior to edit the settings.
Click ok to have the code regenerated.
The code should be regenerated with out the stock column because it no longer exists.
for the checkout failure:
add the following code to the failure page:
<?php @session_start(); var_dump($_SESSION); ?>
that will write the session contents to the page including the gateway response which have information on why the transaction is failing.