I have thought for many years that the restless legs stem from a neck problem that impinges blood flow or drainage to/ from the brain
That's intriguing, as I've had neck issues for decades (including the fact that it sounds and feels like there's gravel in there every time I turn my head. I've been meaning to try an acupuncturist.
-- You've been trying all the right things, IMO. I could never tolerate Flexeril, or understand its purpose, since all stims noticeably aggravate my RLS (as Merida points out with Nuvigil).
The only thing that works really well for me is cannabis -- especially when that RLS feeling spreads to the whole body sensation. It's great for all my neurological symptoms, which all get worse at the end of the day. It also helps for sleep in general, so I only use it about a half hour before bed. I never have trouble falling asleep anymore, but I do still get sleep disturbances in those 3-6 AM hours -- though not with RLS usually.
TENS stimulation, also, I found is quite helpful for RLS. I use it every night for an hour while watching TV, and really notice when I don't. Takes the edge off "burning" feet too.
Finally, a long soak in an epsom bath is my best path to soothing magnesium infusion. I always start my evening with it, but if I didn't have the cannabis I'd try it right before bed, as it's very relaxing.
EDIT: I forget to mention that I like baclofen a lot too when I feel I need some extra help relaxing in the evening. Unfortunately my new PCP says baclofen is now in that category of drugs that require her to drug test me!