Sorry, I can't help you with your Nikon flash setup, I use a Godox for my macro work. I would be interested in your experience and images when you get this worked out. I started taking hummingbird pictures last year, and really enjoyed it. I didn't use flash. I was able to get fast enough shutter speeds to stop the wings, although it did result in high ISOs. Those seemed to clean up very well in post processing.
I suspect that the flash may startle the birds. Also with flash, you will not get a string of images to make it easy to get the optimum wing angle or pose. Still, low ISOs would be very much a plus. Also, I don't know the conditions you are shooting in. I was able to use either full sun, or open shade, which normally gave me shutter speeds equal to my ISO. If you are shooting in heavy shade, or low light near sunrise or sunset, a flash may be a necessity.
I look forward to seeing some of your work. Hummingbirds are challenging, but a lot of fun.