http://198.27.80.217/~vintagep/wp-content/themes/mystile-child/style.css has

#header #navigation,
#header #navigation ul.nav {
    float: right !important;

}

It should be

#header #navigation,
#header #navigation ul.nav {
    float: none !important;
}

according to http://wooexplorer.com/how-to-center-logo-and-nav-in-mystile-theme/

Also STEP 3 of my tutorial has not been followed in http://198.27.80.217/~vintagep/wp-content/themes/mystile-child/custom.css. Do that.