I've yet to experience the problem of the Menu Bar disappearing when using the /load_uisettings command on new toons.
An unfortunately side effect of using this command, is it will copy the stat bar's configuration since it is saved in the UIsettings file.
Make sure you are typing this command with proper uppercase letters:
/show_window MainHUD.StartButton
It's possible that the UI layout that you are "copying" from is screwd up somehow, but I'm not sure why that would be.
As for cures casting twice, this may be a UI bug in which the first button you press will actually trigger twice, but after that it should only fire once. If not lemme know. I use the quick cast and quick cure buttons somewhat infrequently. I'm more of a keyboard user.
As for the chat window, I've had it on the to-do list to make the shadows option save between session, just hadn't quite got to it yet. Look for it next update.