But the shutter speed at F/3.8 was already at 1/8 which is REALLY pushing it hand held/bracing the camera & hand on a post. So again, I didn't feel I could stop down the aperture any more in that situation.
I'm not picking on you phiya, but let's disect your last comment. I'm overlooking that the f/3.8 stat was a typo, as there is no f/3.8 that I know of on a Nikon. Your listed gear doesn't account for a lens that is capable of f/2.8, so I'm not sure what your aperture was, but regardless, I still think you could've stopped down a wee bit further. Then you went on with
"hand held/bracing the camera and hand on a post". That tells me that an opportunity to have rested the camera on the post was an option available to you. Even though this might not have been the optimal framing you wanted, this is where shooting fat and cropping in post (not the post you were resting on, the post processing). By having the camera resting solidly, you could have had an exposure time of 30 minutes if you wanted. This is the crux of the biscuit. Expose for the background and flash for the subject.
I also think the specular highlights in the background are overwhelming and immediately draws the eye's attention rather than the rope. Had you stopped down the lens a bit more, this effect would've been less prominent IMO and would've rendered the background more discernable without overpowering.
It really is a matter of shooting and practice. I don't mean to give you a hard time, but with situations such as this, I may take a dozen different exposures at varying settings. Only by knowing the faults can you find the diamonds. Keep shooting and taking note of the results. That's how we become more proficient. along with a bag full of excuses, I have a boat load of duds. My keeper rate is better than it was, but not nearly where I want it to be. But at the end of the day, I learn something with each click of the shutter.