We wish you strength in your endeavour but please do note that there is no scientific support for fasts longer than 40 days and anything longer than a week at most should be medically supervised with regular examinations and blood tests. Auto-catabolism (devouring your own tissues) may happen insiduously and not be noticed but could be irreversible.
Also note today's article concerning "vitamins", something I practically never recommend anyone taking:
www.express.co.uk/posts/view/134841/Vitamin-pill-cancer-risk-
Remember that we need about 300 nutrients in balance to be healthy. The "Manufacturers" of "supplements" exploits our desire for good nutrition by packing isolated nutrient analogues called "vitamins" in pills or potions. In general it just tends to upset the very delicate balance the body needs and tries to maintain through biofeedback.
Also do bear in mind that during fasting (or as you contemplate, semi-fasting) many cells release toxins, which can damage others. That's why I always recommend active, rather than passive fasting, performing several but at least one cycle of detoxification activities per day.
Isotonic solutions of electrolytes might be beneficial, once again making sure that the balance of inter alia sodium versus potassium and calcium versus magnesium is maintained.
If all of this cannot be well controlled, supervised and checked with regular examinations and blood tests, it is always safer to opt for repeated short fasts. This gives the body an opportunity to re-instate homeostasis on a regular basis.
Best wishes!
André