Its a bad assumption to think that a low light performance camera will deliver in low light conditions.
Cause it will not.
You need 1/60 at least to have a reasonable chance of preventing motion blur and probably around 1/125 to do it really reliably.
This puts a strain on the iso needed, bumping up the iso.
Then you need a reasonable f-stop to have DOF, yes you'd want that to keep ppl looking in focus and help in focus shift due to subject shifts.
Again, that puts a strain on iso and it needs to go up again.
Use a flash, and learn how to use it properly.
Here is a link with many tips on usage.
http://neilvn.com/tangents/flash-photography-techniques/
Know more about your camera too, which comes with practice and read up.
I can give you a 'formula' but it would be irresponsible to do so.
Reason is that it would only work in certain situations and if your conditions are not the same, it may not work.
1. Set camera to M.
2. Expose for the ambient. Guideline is to keep a shutter speed that stops movement and camera shake (eg. 1/80). Iso keep a reasonable iso that is not too noisy and retains detail (eg. Iso 800 or 1000, 1600). F-stop should give reasonable dof too, eg. 2.8, 4.
3. Power on flash on ttl mode. If your flash is smart enough in ttl mode it should expose your subject properly. Adjust flash power compensation to taste. (Nikon flash system supposed to be the best in business). If ceiling is low enough, you can bounce the flash for more flattering and softer light.
Practice this if you can.
Good luck