I believe fasting is ridiculously difficult when not in ketosis or at least highly keto adapted. Even after establishing ketosis there seems to be a period of time where kicking sugar/carb addiction generates serious food cravings, then there's the possibility of carb flu making matters difficult. I think Master Cleanse is foolish and I wouldn't be jealous of anyone deliberately destroying gut flora. They are taking serious metabolic risks, imo.
Getting conditioned to fasting requires some will power. You sound like you may be suffering carb withdrawals. Keep lowering them, eat a big vlc dinner high in fats, and maybe have a late night snack, and try again. It will get easier.