1) on the confirm page, find the following form element:
<input type="hidden" name="item_number_<?php echo $eCart1_Index+1; ?>" id="item_number_<?php echo $eCart1_Index+1; ?>" value="<?php echo $eCart1->DisplayInfo("ID") ?>" />
and change it to use the sku cart object column instead of ID
NOTE: Im pretty sure paypal requires the ID to be numeric.
2) The shipping is recalculated when the checkout page passes to the confirm page.
3) Add the following code on the checkout success page before the </html> tag.
<?php
// Initialize the session.
// If you are using session_name("something"), don't forget it now!
@session_start();
// Unset all of the session variables.
$_SESSION = array();
// If it's desired to kill the session, also delete the session cookie.
// Note: This will destroy the session, and not just the session data!
if (ini_get("session.use_cookies")) {
$params = session_get_cookie_params();
@setcookie(session_name(), '', time() - 42000,
$params["path"], $params["domain"],
$params["secure"], $params["httponly"]
);
}
// Finally, destroy the session.
@session_destroy();
@session_regenerate_id();
?>