Hello,
1) This is because to center the logo you have to set it as a block element but the social icons are meant to be displayed inline. There wouldn't be another way to center the logo without manually editing the index.php file and separating the elements to separate <div> areas.
2) Adding a new position would require custom programming. You can look at our Tutorial here if you are trying to add a new position that isn't part of the Template or Framework.
http://www.shape5.com/documentation/Joomla/Advanced/How-To-Create-A-Custom-Position