Nurse paying blood money for a patient that passed away

Q: I am working as a nurse in a clinic. One day a certain patient came and had been diagnosed with Malaria. The same day he was injected with diclofenac injection intramuscular for reducing fever and other antimalaria intravenous injection also.

The problem is that the place where we injected that diclofenac, that area swelled and the patient showed me after 3 days. On the 4th day he came back with a bad condition. When we tried to investigate other problems, we found he had hypoglycemia (low sugar) and anemia (low blood) but we decided to transfer him to the biggest hospital. Finally he died there.

My question is: what I should do? I am confused since I don't know whether he died because of that abscess or those other conditions he had. My aim is to pay blood money or fast as it is mentioned in the Holly Qur'an if you kill by mistake.

Interest money

Q: I want to apply to study in Canada and for this purpose I need a GIC certificate. A GIC is an account which I will open in a Canadian bank to show that I can bear their living expenses. When I go to Canada, they will refund me my funds within a given period of time along with interest. As a Muslim, interest is completely prohibited in Islam. What should I do?

Does a promise constitute an oath?

Q: If one makes a promise by accident or something they don't want to say comes out of their mouth as a promise to Allah, does the promise have any effect? If a married woman says Allah, I promise not to have sex with anyone and thinks she also included her husband in this, has she promised not to have sex with her husband and will she be sinful to have sex with her husband?

What if a woman explicitly promises not to have sex with her husband by mentioning her husband in the promise. Will she be not allowed to have sex with her husband and will she be sinful for having sex with her husband?