Man, I had many similar problems and tried all these supplements and although they helped in general in other areas
they didn't do a thing in helping with muscle stiffness, weakness, heavy legs, tingling, numbness, cramps, feeling like walking on the boat if you know what I mean.
Finally I got the solution, most of these symptoms appeared to be muscle tensions related, which cause spine/nerves problems. Read that book and you'll never look back: "The Trigger Point Therapy Workbook" by Clair Davies.
Also take few hours of myofascial release therapy.