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?