Marriage terminating with death

Q: I came across that death terminates marriage. But I have seen a hadith that our Nabi (sallallahu alaihi wasallam) said to Ayesha (radhiyallahu anha) that if she dies first then he will give her a bath. Also, Ali (radhiyallahu anhu) gave Fatima (radhiyallahu anha) a bath. Can you give me authentic ahaadith and proofs that death terminates marriage? In afterlife, will husband and wife would be together in jannah. So it is really confusing.

Controlling one's nafs

Q: I cannot control my nafs. It has become so difficult. Especially since I eat too much and I know that I am not hungry and I have a serious digestion problem. I know it hardens the heart but I can't stop. Not only this, in many other matters I have found that I can't control my nafs. What do I do?

Women covering their faces

Q: If the face of women and hands are not awrah then why is it compulsory to cover? Is it a major sin to show the face? You said in one answer that it is compulsory in this time of fitnah... Isn't it compulsory from the era of our Nabi (Sallallahu Alaihi Wasallam) when the ayah came?

Egg donation (IVF)

Q: My husband has two wifes. I have two sons while the other wife has no children. My husband is forcing me to give one of my eggs so that he can produce a test tube baby and put this in the uterus of the other wife. I am not happy with this. Is this allowed in Islam?