Our 25-year old son has suffered from this chronic pain condition since age 21 after incurring a broken ankle. It is now in his left foot, ankle and lower left leg.

Has anyone had much success with RSD?

No, I have no experience with RSD.
But maybe you could place this story on Healing Requests (Only dutch people read this part), so you have a bigger chance that people can help you.

Good luck!

Marijke