Is it necessary to make up two days of missed fasting if a fasting person has a wet dream and delays performing ghusl until after Maghrib, fearing water might enter the throat?

You erred by not performing ghusl, fearing water might reach your throat. It was obligatory for you to perform ghusl when you intended to pray. A small amount of water reaching the throat unintentionally does not invalidate the fast. You must make up the prayers you performed before performing ghusl from janabah. A wet dream does not invalidate the fast.