Please consider working with a dog communicator with this. Posters here have recommended using such a service before .. I was never quite sure about it, but almost 2 weeks ago, I used a dog communicator to help my dog over some issues, and I can only tell you that it was a wonderful and a joyful experience for my dog and myself.
I'll write in more detail later .. but just wanted to pip in with this idea .. as the communicator may be able to help your dog be calm when his nails are being clipped.
Sedation on a regular basis may be harmful. Please consider the dog communicator route as it can not harm in any way.