Thanks Bishop! You nailed most of that.
To make your items float to the left like that, this should help: https://generatepress.com/forums/topic/split-top-menu-into-left-and-right-section/#post-200423
Also, instead of the HTML above, you would just use the URL and Navigation Label fields when adding your custom links.
So mailto:YOUR_EMAIL in your URL field, and LINK_TEXT in the Navigation field.