Hello,
1, 3. Add this code in Theme Options > Styling > Custom css:
.menu-wrapper .menu > li:hover .nav-sublist-dropdown {
margin-top: 0;
top: 65px !important;
}
2. Please check Theme Options > Typography > Navigation.
Read more in doc http://xstore.helpscoutdocs.com/article/86-general-information http://xstore.helpscoutdocs.com/article/27-mega-menu
Regards