Is potassium chloride (common salt substitute) not a solution to this problem?
Yes, in low doses, but in high doese, it’s also the 3rd chemical administered in the lethal injection process:
http://en.wikipedia.org/wiki/Potassium_chloride#Precautions
Yes.
Some manufacturers produce a blend of potassium chloride and sea salt, which has a taste virtually identical to table salt. Also, sea salt has more flavor per mg of sodium than table salt, so you end up with a product that tastes just like table salt with one-third the sodium.