Hi Benjamin,
Regarding the name display format setting, I've added the missing setting to EasyBlog backend under Settings -> Layout -> General ->Display settings the 'Name Display Format ' at your site. I've then configured the name display format to 'username'. Now your site is showing username instead of real name
For your information, the Backend -> Categories -> [select the category] -> Post Options the author name display setting will be removed as this setting now become a duplicate setting in EasyBlog
The fix will be included in next release of EasyBlog
Hope this help and have a nice day!