Hi
1. You can put the shortcode in the [center width=”total width”]…[/center] as below
[center width="120px"][van_social_icon color='light' facebook="http://www.facebook.com/ThemeVan" twitter="http://www.twitter.com/ThemeVan" dribbble="http://dribbble.com" tumblr="http://themevan.tumblr.com"][/center]
You should replace 120px to the actual total width of all the social icons.
2. Yes, in currrently, the br tag is filtered out by the code. Or temporary try to use custom CSS to line break as below
this is the first line
<span style="display:block;width:100%;">This is the second line.</span>
Thanks!