I have similar problems as your husband. For years, I have had very strong, jerking and kicking of my limbs. It's not really RLS, more like uncontrolled spasmodic episodes which I am not aware of unless awakend by my spouse. I also have severe night sweats. I served in Vietnam with the Marine Corps as a Hospital Corpsman 67-68 and while I never remember actually handling agent orange, I know that the entire hill I was on was totally denuded of vegatation which never grew back. I also use an unknown, unmarked chemical which I mixed with diesel fuel and sprayed around the "outhouses" to keep weeds and insects down.
Besides my night time episodes I have joint pain in my shoulders, arms, feet in varying severity most of the time. (no history of injuries and I do not do a physical job)
Could it be Agent Orange? I don't know... but if you ever find some treatment for his jerking at night...let me know. i've tried everything from quinine to anti-anxiety medications. I would be greatful and so would my wife!