What is the ruling on the fast of one who was ignorant of the things that invalidate fasting, such as masturbation and the emission of semen or prostatic fluid, and fears not being able to fast for two consecutive months or feed 60 needy people?

Whispers concerning swallowing water do not invalidate the fast. There is no need to make up past prayers unless one is certain that something requiring ghusl (ritual bath) was emitted. For one who doubts whether something was emitted or not, the default is that nothing was emitted. It is necessary to make up prayers that were performed without proper ritual purity.