Layout destroyed after inserting a widget in <div class="menu-container">

I like this theme very much. However I have to change it for my purpose. I need a cool main menu than the default effect, such as the Mega menu in 1.png:

But it is a widget, so I added the widget by replacing <?php inkthemes_nav(); ?> in header.php with <?php dynamic_sidebar('my_mega_menu'); ?>.
Now, the menu appeared but the page layout below the main menu position is destroyed!!

I always tested that put just a search widget instead of the Mega menu widget. The problem is the same.

Before using a widget in "menu-container" position, the layout is correct:

Could you help me? http://223.4.158.139/
Thank you.

 

The menu widget I used is jQuery Drop Down Mega Menu. Adding A Widget Area To Your Theme Files following http://www.designchemical.com/blog/...ial-adding-a-widget-area-to-your-theme-files/