Spotting after the haidh period

Q: My question for today is I did ghusul on 18th of May but from 23rd I am spotting blood and despite spotting blood I was still praying and on 26th I was fasting again despite spotting blood. I told one Muslim lady and she told me my fasting is makrooh, so I had to open my fast. I didn't pray on the 26th till 28th but I did ghusul and I am fasting on 29th but in the morning again I spotted blood so I just wanted to know am I allowed to fast and pray despite blood spotting or not?

Doubts regarding urine drops

Q:

  1. I suffer from droplet problem. After passing urine I wash and put toilet paper till all the droplets come out. However sometimes the toilet paper moves out of place. Does this make my underwear napaak and do I have to wash it?
  2. Previously I should ignore this and thik it to be waswasa, I have led quite number of salaah as imam in this state. How do I make up for all the musallis salaah that was read behind me?

How should one discharge fidyah?

Q:

  1. When you donate money to charity organisation they have box for Zakat, Lillah and Sadaqah,which box should one put the Fidya money(money for fast missed in the month of ramadhan due to long term sickness) and Kaffarah money?
  2. Is it permissible to give Fidya money (money for fast missed in the month of ramadhan due to long term sickness) to a poor person but not very poor because he can not take zakat money?

Interest

Q: Interest is considered to be a strong haraam and a grave sin, but isn't interest needed as a fundamental basis for starting a bank and being able to
hand out loans?