Your ticker is contained within a div with a class of “et_pb_row” (which is part of your theme’s css). Your theme css has that class set to a width of 1080px which is why the ticker is not expanding wider than that.
You either need to remove any of your html wrappers that have a set width, which looks like you should put it directly in the .et_pb_section div, which does expand full width.
I have no idea how your theme is built or how much control you have over something like this (without modifying the theme), so that’s about all the instruction I can give you on this matter.
You can center the ticks by adding the following to the custom css field on the News Tickers > Settings page:
.mtphr-dnt-tick { text-align:center; }
The size of the black background and white space underneath is also due to your theme’s css styling and how it adjusts depending on the page width. The ticker is not changing size, but the containing element (that has the black background) does. I’m not seeing any easy way to adjust this as the surrounding divs do not have any unique id’s or classes… so, if I have to code to change these, they would change every instance of the classes throughout your whole site.
I would suggest contacting the author of the theme to find out a good solution for modifying the css for this particular area… Or the easier option, would be to not place the ticker within one of the .et_pb_section areas and just place it in a place it directly under that blue header section (if you have that ability)… then, if need be, you can style the main ticker wrapper which does have a unique id, if you want to add a black background and what-not.