It looks like you are using the OrderID column from the orders table as the Order Number.
in the database this column should be set to auto increment so should not be able to use the same value twice.
perhaps in the confirm page, change the following code in the store order summary behavior
$_SESSION[$WA_sessionName] = mysql_insert_id();
$insertedOrderID = mysql_insert_id();
to:
$_SESSION[$WA_sessionName] = mysql_insert_id($WA_connection);
$insertedOrderID = mysql_insert_id($WA_connection);
As for the Recurring payments, we could help implement this in a premiere support appointment.