Hello Leon,
Thanks for asking. 
Looks like you have already made couple of changes. You an add following CSS under X > Theme Options > CSS to further mimic Integrity 1 navbar styling:
.x-navbar .desktop .x-nav > li > a:hover, .x-navbar .desktop .x-nav > .x-active > a, .x-navbar .desktop .x-nav > .current-menu-item > a {
box-shadow: inset 0 4px 0 0 #84d64a;
}
.x-navbar {
border-bottom: 1px solid #ccc;
box-shadow: 0 0.15em 0.35em 0 rgba(0,0,0,0.135);
-webkit-transform: translate3d(0, 0, 0);
transform: translate3d(0, 0, 0);
}
1- I have found the proper CSS code selector using the Chrome browser Developer Toolbar: https://www.youtube.com/watch?v=wcFnnxfA70g
2- For the CSS code itself, I suggest that you get started with this tutorial: https://www.youtube.com/watch?v=yfoY53QXEnI
Thanks.