If you have the chance, don't forget to taste the Korean "flower salt", which is basically salt in crystal flakes, as it naturally forms during evaporation. I haven't yet found a better salt for beef.
A favourite of mine are "Maldon Sea Salt Flakes". Not sure if it is actually "fleur de sel" but it is truly delicious and available almost everywhere (for instance through amazon...)
Sure, as long as you don't claim its magically more healthy than other forms of NaCl. Not saying you do; just seen that regularly claimed by people who prefer/swear by certain salts.
I don't make any health claims; however, un-processed salts, such as Celtic Sea Salt contain much more than just sodium. They contain many other minerals.
In other words, Celtic Sea Salt is more than just NaCl.