Resting is good during a water fast, its helpful to the fasting process.
As for how long the fast will be - you won't go beyond the return of hunger which can vary in length for each faster and each fast.
It depends on how much nutritional reserves a persons body has and the degree of work to be done by the body during the fast.
Here's some reading on the subject and a quote from it.
http://soilandhealth.org/02/0201hyglibcat/020127shelton.III/020127.ch23.htm


"" A 'finish fast' does not always mean a long fast. It does not mean a fast until all of the body's food reserves are exhausted. It is a curious fact that hunger will return in three days, even where there are abundant reserves on hand, if three days are all that are required for the patient to get well; whereas, it will not return for five weeks or longer, even where there are fewer reserves on hand, providing this time is required for the body to eliminate its accumulated toxins. Fortunately, in most cases it will be perfectly safe for the patient to fast until hunger returns.""

Um, a 100 day fast does seem a tad excessive for a first time unsupervised fast. The mormon woman who was reported to have lost that weight was medically supervised on her 90 day fast and lost 150 pounds in that period, which is 10 pounds more than what you weigh. She was still obese at the end of it.

Assuming your figures are accurate, if you want to get back to a healthy 13% body fat, you only need to lose 25 pounds so that works out at 25 days fasting total. Your BMI will then drop to around BMI 17 I should imagine, and come back up to the slim 18.6 which is what you were at 115 pounds. Currently your BMI is 22.6.

Of course the other way to decrease % fat is by increasing bone and muscle, and exercise is the only way to do this. Exercise will also help with depression.

Think about the pros and cons of everything, and decide what's best for you. You might want to kick start the changes by fasting then re-asses later. As Donn says, you should rest when fasting.

I agree with mouseclick 100%. You would shrivel away fasting for 100 days.

Even some of the most experienced fasters on this forum have only done 30 to 40 days at the longest, maybe a few longer, but be realistic, and don't jump into something you are not educating yourself about properly.