Popup Button Placement Options

Hey - so I've been struggling to use my own button shortcodes in the body of the text, so I am using the button you guys make available by default.

The problem is it looks good on preview, but when I try it on the live site the button is out of view.

I attached a screenshot to show you how it looks live.

A solution would be great - and also would love to know if I might be able to 1. bold the font in the button and 2. possibly center the button in the box?