Let's rename edd_email_tag_name() to edd_email_tag_first_name() to make sure it's very clear which name it retrieves.
edd_email_tag_receipt_id() should use edd_get_payment_key() instead of pulling it from payment meta.
edd_email_tag_payment_method() should call edd_get_payment_gateway() instead of using get_post_meta().
edd_email_tag_receipt_link() should also call edd_get_payment_key() instead of using payment meta.
The address info in edd_email_template_tags() needs to be removed.