Display main menu expanded in footer, drop down in header
We use the menu_block module for this - it lets you create unlimited menu blocks and control menu depth and other options.

This module provides configurable blocks of menu links with advanced features not available in Drupal 8 core.
Drupal 8 core allows you to display blocks of menu links starting with any desired level of a menu and limited to any desired depth.
And this Menu Block module provides additional configuration so you can choose to expand all menu links with children or to root the menu tree to a specific menu item.
The Drupal 7 version of this module provides all of these features since Drupal 7 core does not have any of this functionality.

So I just noticed you're already using menu_block. You can add multiple_menu blocks - you should simply be able to add a new menu_block for the main-menu on your site and use that one in the footer.