Hi,
the megamenu is included with the theme.
When you go to create a new menu that will be a megamenu dropdown, first you add the link (or a page) that will be your megamenu. Then you save the menu. Then you open the menu (that page you added, see the picure below) and you can choose in the Menu Type what kind of menu it will be (Default standard, or Mega Menu with the columns).
After you choose what kind of menu it will be (how many columns it will have), you can then add your submenus and submenu items within them.
For second questions we send you screenshot, you can see that second test pages(subitems) are aligned right.
I hope this help you.
Cheers
