I think your shots look great! You should be able to shoot at ISO400 all day long with your D7100 without any noticeable quality loss. This will help with your flash recycle time. I shoot an SB910 for main, SB700 for fill, and SB600 (newly acquired) for hair light/background light.
As stated, you can also push your lights in a little tighter to your "model"...if you are shooting in TTL then you won't have to adjust anything, the camera will make the flash power adjustment for you. If you feel the exposure is a little hot, you can dial in - 1/3 flash exposure compensation and take another shot.