I went through all of your pages and updated the paths so they pointed to the correct folder.
Then I went through the checkout, but I changed the trigger so the email is sent before the purchase is made.
I got the email and didn't see the error you reported.
I did have to update:
$Email->BodyFile = "webassist/email/templates/wa_receipt3.php";
$Email->BodyFile = "webassist/email/templates/wa_receipt.php";
Since wa_receipt3.php wasn't uploaded to that folder.