I can't/won't use a Joomla file browser to change files. If I change something that breaks the admin, I have no way to fix it.
So if you can provide direct (s)ftp access, I am happy to look into this further.
But I must say: You have an enormous amount of data on a single page, because of the many nested tabs.
This makes the page load and react pretty slowly.
I recommend thinking about re-organizing the pages.