Doubting making a vow

Q: One year ago, I began to suffer evil whispers that drove me to supplicate against people unconsciously inside myself. These whispers troubled me a lot and later developed into words of Kufr (disbelief) if I uttered them. My condition got worse and unbearable, and therefore, I vainly tried to find the causes of such whispers. One day when I was reading in the Mus-haf (copy of the Qur'an), my eyes caught the Ayah (Qur'anic verse), which reads: And of them are some who made a covenant with Allâh (saying): "If He bestowed on us of His Bounty, we will verily give Sadaqâh (Zakât and voluntary charity in Allâh’s Cause) and will be certainly among those who are righteous." (Part No. 23; Page No. 367)  Then when He gave them of His Bounty, they became niggardly [refused to pay the Sadaqâh (Zakât or voluntary charity)], and turned away, averse. So He punished them by putting hypocrisy into their hearts Upon completing the Ayah, I thought that I had made a vow and did not fulfill it, and this was the reason behind these whispers. I tried hard to remember that vow to the extent that I doubted that all my acts of worship might be a vow. Finally, I decided to regularly observe performing all the voluntary acts, such as voluntary Salah (Prayer), Qiyam-ul-Layl (optional Prayer at night), making Wudu' (ablution), giving Sadaqah (voluntary charity), like the obligatory acts. I did so for fear that I might have become a hypocrite - Allah forbid! I was under the impression that such whispers might result from unfulfilling a vow. I performed Hajj after which I got sick and suffered a severe fever that awakened me and was accompanied by such whispers. At this moment, I was sure that the whispers possessed me due to the lack of fulfilling a vow - and that is hypocrisy - and the severe fever was punishment from Allah for that. I remembered the punishment in the grave and felt that I would die of the severe fever. Having used cold water, the temperature decreased, my body cooled and the fever was reduced. Before being transferred to the hospital, I made a vow to say, "There is no god except Allah Alone. He has no partner. To Him belongs the dominion, and to Him belongs [all] praise. He gives life and causes death, and He is Able over everything." a supplication that (Part No. 23; Page No. 368) the Messenger (peace be upon him) said on the day of `Arafah. I vowed to say it one hundred times in the morning and one hundred times in the evening since sins of the person who does so will be forgiven even if they are like (as many as) the foam of the sea. Also, I made a vow to memorize the Qur'an since Hell does not touch a person who memorizes it. If I died, I would get the reward of these acts; otherwise, I would fulfill my vow. I hope to be saved from punishment in the grave and on the Day of Resurrection by doing so. Later, I got to know that I did not make a vow and the severe fever was not a result of an unfulfilled vow. Also, the Kufr-related whispers were cast by Satan. As I received treatment, the whispers began to disappear. Is my vow effective? Does it require a Kaffarah (expiation), knowing that I made that vow in my full senses? Is it obligatory to fulfill it?