Welcome to the forum.
Regarding the salt question: I do not have any facts or figures but I know that the amount of salt needed depends completely on the weather/temperature and the amount you are excerting yourself. For example about a year ago I did a hike with a group with huge heavy bergans on, in hot weather. We all made sure we drank lots of water to stay hydrated. However one of the lads started to go downhill as we reached the end of the hike and when we reached the final destination we had to carry him as he was almost colapsing. This was all due to drinking lots of water and sweating. This just washed all the salt and minerals out of his body. We gave him a strong drink of orange squash with salt and sugar disolved in it.

Hope this helps a bit.