1) Only thing I can suggest is trying to override with css:
nav.mega-menu ul.menu > li.menu-item:hover > .mega > .sub {
display: block!important;
}
2) That isn’t what I was referring to, you’d need this css:
.header-6 .container {
width: 100%;
}
.header-6 nav.mega-menu li .sub-container {
left: 0!important;
width: 100%!important;
}
nav.mega-menu li .mega .sub, nav.mega-menu li .mega .sub > .row {
width: 100%!important;
}
That should sort it.
– Ed