I don't think there was anything wrong with your first set of images. If the second set at a faster shutter speed looks better to you, the initial problem was either *subject movement (very possible, given the subject) or *camera shake (also possible.)
Are you using VR or a tripod?
At those apertures your plane of focus is going to be very thin. Any kind of motion is likely to move your focal plane to somewhere you didn't intend it to be.
working on it in Middle TN Nikon D3100
35 mm 1.8 Nikkor 18-55 mm Nikkor VR 55-200 mm Nikkor VR 55-300 mm Nikkor VR 150-500 mm Sigma OS Feisol CT3471 & Markins M20 ballhead
I think you are right about the possible movements causing some blurriness.
I expected the flash to freeze any subject to camera distance changes and movements of the subject. I guess there was enough ambient light so the exposure took the full 1/60 sec as the flash was not the main source of light.
The lens is NIKKOR 35mm 1.8 so there is no VR and I did not use any support, it was hand held.
The next time I will try to shoot in manual mode 1/200sec at f2.8 (hand held) I think it should work.