There is no danger in a high level of ketosis PureH20; full ketosis occurs after 9 to 11 days when muscle wasting is at a minimum, in what is known as "protein-sparing". Full ketosis is when the max' ketone bodies are being manufactured.
The return of genuine hunger is a rarity these days, but the primary reason as to a fasts need to be terminated. This can occur at anytime, and depends on the levels of toxemia/the amount of healing needed by the body, and the quality of food reserves still available. However, nutrient-deficiencies have been known to occur after 21 days (potassium) and other electrolyte deficiencies after 40 days.
Your BMI is on the underweight side, so please be careful as to how much longer you intend to fast.