Cannot update to 4.3.1, Load Customize, or insert images

Hello,

I am using WordPress 4.3 and the Customizr theme on my site.

I am experiencing a few issues:

I cannot insert images into posts/pages. The buttons/tools that would enable me to do so have disappeared.

I cannot load the Customize screen. It takes me to the customize page, but nothing appears in the menu, a Fatal Error displays across the top of the screen, and the spinning ball just keeps spinning.

I cannot update to WordPress 4.3.1. When I attempt, I get this message:
‘Could not create directory.: wp-includes/images/crystal’

Any help would be much appreciated!