Classifieds Credits System inquiry and feature request

I recently installed Classifieds to try out and I really like the simplicity of it. I also am really interested in the credit system.

I read another thread in here about users inadvertently getting the ability to create unlimited listings - I was wondering if this was possible to configure on purpose.

Suppose I have 2 different groups of users. I want one group of users to have to purchase credits normally in order to create listings. I know I can't mix free listings with credits, but would I be able to set the other group of users to bypass the credit system somehow? (Being logged in as an admin users bypasses this it seems, but obviously I can't make them all admin users)

Alternatively, I would like to request the admin ability to send credits to a group of users rather than just one individual user at a time.

Thanks in advance