One of the errors looks to be down to Prettyphoto, the lightbox built into the theme. Now that theme dates back to 2011 - it’s not even responsive - so it could be that the age of the theme has finally caught up with it.
My first port of call would be to see if the developer - BLT (http://bltthemes.com/themes/) is prepared to take a look. Longer term, I’d think seriously about rebuilding it with something more modern. It’s a nice site with lots of good content and wouldn’t be too hard to bring up to date.