Hi there,
1. You can use a header widget in “Appearance > Widgets”. If your current header is a full width image, you’ll need to sit the widget on top of it with code like this:
.inside-header {
position:relative;
}
.header-widget {
position:absolute;
top: 20px;
right: 20px;
}
I usually advise against this as absolute positioning can get a little wonky on mobile, but there’s no other alternative if the header if a full width image unless you add the text to the image itself.
2. This thread should help: http://generatepress.com/forums/topic/social-networks-buttons-on-nav-menu-bar/
3. You can use the Page Header add-on for this. Set up your slider using your preferred slider plugin – most of them have a “Force full width” option. Then add the shortcode to the Page Header Content area.
Let me know if you need more info 🙂