Yes I do. A higher ISO should have increased the effectiveness of your flash.
There is some red-eye going on caused by your on-board light, but that is not what you are asking about.
There is a lot of information on this forum dealing with high ISO shooting. And a lot of it gets really technical. So I won’t repeat all that.
I just did a
high ISO shoot where no flash was allowed and here is basically what I did. I set my lens wide open with the camera using Av. I see you shot using Av as well. At lower ISO’s I was getting a painfully slow shutter speed so I started upping the ISO value (ended up with 3200) until I got the meter zeroed and a shutter speed I could live with. As you increase the ISO, your shutter should speed up provided the aperture stays the same. I would have liked to get a smaller aperture (larger number) but I wasn’t sure what my camera would do at a higher ISO. I didn’t want to go any higher than I absolutely had to.
The critical part is not to under-expose. By doing so you help to keep the noise under control. So I increased the exposure compensation as much as I dared, which in Av simply means the shutter slows down to let in more light. Checked my histogram with the idea of getting everything over to the right. That’s pretty much the procedure I used for the camera settings. I don’t know much about Nikon cameras but you could still keep the flash in the mix I’m guessing. Just practice up on your red-eye removal because you are going to get a lot of it with your on-board light.
Now, you need to know what ISO your camera will shoot that you find the noise acceptable. I have one camera that I don’t like to go over 1600. I have another one that I’m not really sure of yet. I know it will do 3200 very nicely so I haven’t found the ceiling on what it will do comfortably. The only way I know of to get this info is just shoot in low light, review your results and decide what you can live with.
Other solutions (read: more expensive) would also include some noise removal software and a hot shoe flash gun with a tilting/revolving head. To get away from your camer’s on-board and so you could use bounced light. If I were going to be doing a lot of this type of shooting, I would try a flash bracket/aforementioned flash gun and I like the Fong Lightsphere. Other folks use different types of reflectors/diffusers.