It is at the moment impossible to change any of the settings except for spawn protection and command blocks. The other settings keep resetting back to former or puts you on peaceful difficulty if trying to make the realm/world into a survival one.

I am using the latest version of the launcher like most others and I am also using the latest stable version of the game.

It appears to be related to the errors other people have reported since what I can tell was yesterday. (Error 500) although the error message has been resolved the problem has not been.