Well, like I said sRGB is "safe", although not optimal for everything. One key consideration is when you are saving an image for the Web -- it should be converted to sRGB (using Edit/Convert to Profile) before saving, although Save for Web will also do that.
As for your Color Preferences settings, I'm not too clear on some of what you are describing. Is the camera set to aRGB or sRGB? It looks like it is a Nikon set to AdobeRGB (aRGB) -- is that correct?
If so, make sure you don't assign it to sRGB but only convert it to sRGB (if you do decide to go that route).
Now, I will say that if, like you said, you have been happy with your prints so far, then take this slowly to make sure that you don't end up with an unpleasant surprise by making a bunch of changes then getting a bad set of prints!