Hello,
Please add this code in your child-theme/functions.php file:
wp_enqueue_style( 'dynamic-css', get_stylesheet_directory_uri() . '/dynamic.css' ); http://prntscr.com/kqreis after that create an empty dynamic.css file in child theme directory.
Then custom css from Theme Options will work fine.
About the problem with the menu – Try to disable 3-rd party plugins, clear cache and check how it works then.
Regards