Calling oneself a disbeliever

Q: Please give me the ruling regarding the following: 

Question: In order to convince someone of something, someone said, for example, "So-and-so does not have a car. May I be a disbeliever if he has!" Is it considered to be an oath?

Answer: There are two rulings on this issue:

1. If one says, "So-and-so does not have a car. May I be a disbeliever if he has," the relevant person becomes a disbeliever whether that person has a car or not. One's intention does not count. That is, it is not valid.

2. If one utters something that causes disbelief with the intention of taking an oath, he is considered to have taken an oath. However, such an oath is not a Muslim's oath.

Marital problems

Q:

1. I would like to know what is the punishment for a man who does not treat his wives equally?

2. Also a man has taken a second wife. She is a divorcee and her first husband was having an affair with a woman of disrepute. Now the first wife is very concerned about herself with regard to her H.I.V status. Does she have a right to request that the second wife take a test and that she is shown the results before continuing relations with her husband?

Remedy for doubts

Q: There's a thing that is troubling me a lot. I'm a person who has not much knowledge of Deen and is also stricken with waswas. My waswas were in the form of really complicated questions, about Allah's attributes, whether something is in Quran/Hadith or not, whether this thing is attributed to the Holy Prophet (Sallallahu Alaihi Wasallam) or not etc. I used to note these down in my phone so that I'd ask someone about these, and that caused the questions to increase that I have this answer in my mind, what if I have done kufr. Then I used to say that Ya Allah if any of this is kufr, forgive me. Is that the right thing to do? Also should I delete all these questions from my phone or seek answers for them in case I have unknowingly done kufr?