I have done water fasting for years including several 30 day distilled water fasts, but never dry fasted. From what I gather it has something to do with the spiritual aspect. Other than that I never understood why one would dry fast as the idea behind fasting is to cleanse the body, and drinking distilled water while fasting helps in the elimination of what needs to be expelled.
I can only surmise that the dry fasting didn't do that and that's the reason your tongue still had crud on it. You also might try doing a liver cleanse prior to fasting.
As for ther bloating from drinking only a half glass of water I would think that this has something to do with strengthening your stomach area through exercise. Fasting might lose some fat for you, but will not strengthen your core.