-What I'm not sure of is how much water should I drink? Isn't it calculated using body weight or something?
Drink when you feel thirsty. If you aren't thirsty, don't drink. That's what our ancestors did before they had internet forums advising them how much to drink! :)
-Is it okay to salt water flush (1 liter of hot water with 2teaspoons of salt) during a water fast? If so, how often can I drink it?