Thanks again Jason. Just an status update on my problems:
The loader that changes to the credit card information works fine now. I still experience the trouble with the loader that changes after submitting the order which obviously can only be reproduced in a live or test mode using a real credit card. It keeps spinning and does not change to the checkout_success.php page but the order goes through. I am not sure whether this might be a problem on my local machine or somehow in the template. So I will continue to test this and see whether it is only an isolated problem with some of the machines in our office.
The second problem with the additional email recipients not being send: Adding the additional RecipArrey in the confirm.php page did not work for me and the problem seems not to be the smtp server since we checked the server and there are no outgoing e-mails or any type of sending attempt in the mail server other then the the email being send to the customer.
Anyway - I noticed that there are not BCC or CC entries added by the Universal Mail behavior in the waue_confirm.php page so I added them manually such as:
$WA_MailObject = WAUE_AddBCC($WA_MailObject,"email@example.com, firstname.lastname@example.org");
which seems to work fine.
So I am good for now.
Again. Thanks so much for all your help in this regards.