There's not a way that _I_ know, but that doesn't mean there isn't a way.
I use nvidia-settings too, and every time it offers to do something for me without re-starting X, it fails, and I need to restart X anyway if I want to see the change. I use nvidia-settings more like an info source than as a tool for actually doing something to the server.
NOTE: in my first reply, the command I gave to start X in a second tty, does not kill the running session, it just starts a second one; so for example, if you're using the machine, and you want to lend it to your friend or whatever to watch TV, you can start a second session for the friend, while leaving your first session intact; when the friend is done, just log out of that session, and you will be returned to your own session (or you can switch back and forth any time with CTRL-ALT-[1-7])
Sorry I can't give any specifics about your exact question regarding nvidia-settings, but I hope this info has helped you in some way