But part of my problem is, all of the config files are horribly mangled in Notepad, looking like someone wrote everything on a single line and poorly wrapped it. It's impossible to discern where a line begins or ends.

Opening it in other text editor files produces something legible, but I'm worried about if saving a config file in something like OpenOffice Writer would somehow bork it and prevent DOSBox from reading it.

So I guess my question is, is it safe to edit in OpenOffice Writer, or should I download something like Notepad+ or Notepad++ to do this?

Notepad++ gets my vote. Of course *nix line endings display find in Wordpad and DOSBox can read both *nix and/or Windows line endings.