@Brian:
1. You can add the following css in “Appearance => Customize => Theme Options => Custom CSS Options” box to center the site title and tagline.
#site-branding {
display: block;
text-align: center;
width: 100%;
}
#site-header {
width: 100%;
}
2. There is no option to break the tagline in two separate lines. There is only one option to break the content with the fixed width. You can try adding in the following css in “Appearance => Customize => Theme Options => Custom CSS Options” box
.site-description {
display: block;
margin: 0 auto;
width: 220px;
}