Marrying one's ex husband who wants to accept Islam again after becoming an Atheist

Q: I'm a Muslim and my husband left Islam a year ago and became an Athiest. Since then I am living seperately from him and tried my best to bring him back for the sake of our kid. Now he wants to become a Muslim again. I want advice on what should I do in terms of Islamic law since our marriage was over when he became an Athiest. I want to reconcile as well. But whats the procedure for me and also for him to return back to Islam?

Validity of nikaah if mahr was not mentioned at the time of nikaah

Q: Zaid conducted the marriage of Zainab to Shuaib. But Zainab did not appoint Zaid as wakeel. However Zainab heard the ijab and qubool through the phone and then later when she was asked whether she accepted the nikaah with Shuaib, she said that she accepted. However, she did not notice what was the amount of mahr which was mentioned. So she has no idea about how much mahr she is going to get. Is the marriage valid?

Finding out one's zakaat date

Q: Before I got married, my parents used to pay my zakaat. They used to pay it in Ramadaan.

After I got married, for 3 years I never worked out my zakaat in Ramadaan and it got left till last year. On the 1st of Zul Hijjah, I went and got my jewellery weighed and sorted out my zakaat. Gold was at its highest that it has been in years that time so I paid that amount for all the years as the jeweller said that it will be higher than the other years that I never pay. Alhamdulillah I payed off everything last year. I wanted to know for this year, am I supposed to calculate my zakaat in Ramadaan or should I now calculate it on the 1st of Zul Hijjah?

I did not calculate it in Ramadaan this year as I thought I should value it that same day as I did last year.

Performing qasar salaah when staying in a place for less than 14 days

Q: A person went to a city intending that he will stay there for 14 days and was performing qasar salaah alone until he noticed his wife and mother were performing full salaah. He told them that their stay in the city was 14 days and they should perform qasar salaah.

1. Is it correct?

2. I also heard that the intention of a man is counted if he is with his family. Is it correct?

Children born with disabilities due to marrying in the family

Q: In Islam, is cousin marriage allowed?

Medical science says that cousin marriage is wrong because it causes disabled children. Yes, there are many cases where children are completely fine but there are many cases where children are disabled because of cousin marriage.

My Conclusion: cousin marriage is risky.

Please advise me whether we should do cousin marriage or not? If your answer is yes then how can we overcome this risk?