ssh complains when the permissions on .ssh/config are too lax because that file can't be trusted anymore. Somebody could maliciously add an entry in your config so that "server" pointed to a custom man-in-the-middle IP address, so the next time you ran "ssh server" it actually connected to their system instead of the one you expect, and they intercept your password.
All you accomplished by changing the owner to root was preventing anybody from being able to use the file or directory, including dp3. You might as well have just deleted the file, it would have accomplished the same thing.
Right now it looks like the permissions on your home directory are set to 777. That means ANYBODY who has access to your computer under any account can create, delete, or modify ANY FILE in dp3's home directory. There has to be SOME reason you did this (destroying the security of your user's home directory in the process). Whatever that reason is, it was wrong, there is a better way of doing whatever it is you were trying to do. So change your home directory's permissions back to 750, and I sure hope this is a single-user machine, otherwise everything in your home directory has been compromised.