Fasting is simple, drink as per thirst, rest and stay warm. By taking vitamins you are putting your body in starvation mode. You are taking partial food where your body tries to take additional nutrition from your reserves to digest what you ingested.
You are drinking way too much water. For dry lips and skin you can apply coconut oil. Also take Epsom Salt and Sea Salt bath or foot soaks. This will get some minerals in your body.