I tried to reproduce the issue of adding items in a new instance of omeka, but that seems to work fine.
Given that the stylesheet seems to be missing in your case, can you try if hard refreshing the page in the browser fixes the issue? Maybe this is a caching problem.
Otherwise do you see any errors in the app logs on the server side? It could also be, that the app is crashing and thus not serving up the css right after the crash while it is restarting.
For the CSRF issue in safari, unfortunately I do not have access to a safari browser to test this. Chrome and firefox seem to work fine. here.