Shelton is still the best source for information on fasting and the fasting process, and he never advised supplementing with vitamins as this can lead to malnutrition and deficiency diseases: this would explain your hunger up to day 7 and beyond of course as you were essentially on a diet and a deficincy diet come to that. Not advisable by anyone experienced with fasting supervision.
Prolonged or extended fasts were usually undertaken in remedying a health-malady or disease, so I am curious as to your motivation apart from losing a bit of weight. Shelton and other supervisors found that extended fasts are far more effective in cleansing and healing than a series of shorter ones, even if of the same number of days.
With todays quality of food reserves as they are, a 40 day fast can easily result in an electrolyte deficiency, but that will entirely depend on the quality of your food reserves, and therefore your pre-fast diet.
The omentum will reduce in size or fat content while fasting, but this can also be accomplished via a nutrient-dense but low calorie diet: a diet where you can eat with impunity and still lose weight. This is especially true if it is properly combined and you avoid protein with starches at the same meal.
Although fasting is very safe, it still carries risks and why self-supervision should be properly carried out throughout. I would read the FAQ's and advice at the top of this forum as well.
The post-fast gain in weight can be regulated by the body which seeks to optimize this, but people gain excess weight post-fast because of their return to a less than optimal diet containing too many empty calories or "foodless foods"
I would advise you to research and read up on the term "Nutritarian" where that way of eating post-fast will provide you with optimal nutrition that is also low calorie, and wheer any excessive weight gain is avoided and health is improved immeasurably.