Your first screenshot is from editing a template, but the subsequent console logs aren't actually from that.
Looking at your latest screenshots, it's clear that the default style isn't being used. Loading your site, I also see what appears to be a large number of add-ons (based on the number of queries; you shouldn't have debug mode enabled though). There's evidence of this in the console screenshots as well. Further, your site appears to be running 1.1.5 which is a very outdated version.
The absolute most important thing is to disable all add-ons in the control panel and create a new, totally unmodified style to start debugging. All testing needs to be done with that as a basis.
That said, it's likely there's a server issue here. I suspect if you rename your .htaccess file temporarily, you may get a different error (probably one that implies mod_security is at play).