Maybe go with half a teaspoon to see if that will relieve your RLS just as well as a full teaspoon? Sounds like one teaspoon exceeds RDA for potassium. It's interesting that it's also a laxative. It begs the question whether the potassium is relieving the RLS or the laxative effect? Since it works for you within 20 minutes of consumption I assume it's the potassium and the highly absorbable form that it's in that is providing relief.
Also, remember the source of the article, I would double check the RDA from a more scientific source.