PopUp Pro further customisation

Hello,

I would like to further customise PopUp Pro. What exactly I want to achieve is:
1. Would it be possible to center the button?
2. Would it be possible to change the background of the main content or make it transparent?
3. Would it be possible to change the size of the button?

I searched the other tickets and I found one solution for Issue 2. I used the following code in order to make the background transparent but it didn't work:

#popup .wdpu-msg-inner {
    background: transparent;
}

#popup .wdpu-msg {
    box-shadow: none;
}

Kind regards,
Radoslav Mitov