Stopping one's Kaffara fasts due to an infection

Q: I have been fasting for my kaffarah for about 11 days out of the 60 so far Allhumdulilah. The thing is I have a problem with constant release of Mazi. It is most likely due to an infection. My question is that when I go to the doctor and get the 7 day antibiotic is this a valid Shari reason to cause a break within the 60 days. It's not fully constant all the time but it's enough to make a person change his clothes at least once a day.

Taking an oath that if one breaks an oath, one will become a kaafir

Q: My question is that I had asked one mufti that if a woman takes an oath that "if I do this or do not do this I will become a kafir forever"and breaks the oath will she become a kafir. His reply was that ulama have said that she will become a kafir. But you had said that she will not become a kafir. Please reply I am very disturbed.

Discharging the zakaat of previous years

Q: One has not paid Zakaat for a number of years. I'm now calculating the Zakaat for the current year. How should the liability in respect of Zakaat not paid previously be treated? Does one need to add the outstanding amount to debts and liabilities for the current year and the total amount then be deducted from one’s total Zakaat assets? If this procedure is correct, what then if, after deduction, the total amount does not reach nisaab? If the liability in respect of Zakaat not paid previously is not to be included in debts and liabilities for the current year, can the Zakaat for the current year be cleared immediately and the outstanding amount in respect of previous years be cleared gradually over a period of time?