Ramadhaan & Fasting

Finishing sehri at the last minute following an incorrect clock

Q:

1) Zaid followed his faithful bedroom clock for many years and he used to complete eating his sehri at the last minute based on the time on this clock. He recently compared his clock with the BBC time and found it to be 3 minutes slow. Is he muqallaf of following this time and repeating his fasts considering the possibilty that the BBC or any other central bureau time may also be incorrect.

Fasting so that one's dua will be answered

Q: The Prophet (Sallallahu Alayhi Wasallam) said that the dua of a fasting person is answered. It's borne on the clouds and the gates of heaven are opened for it, and Allah (Ta'ala) says "By my glory, I will grant you help even if it may be after sometime". Can I fast with the intention that my dua will be answered, or is that disliked? Any help will be greatly appreciated.

Sadaqatul fitr

Q: Please clarify the following:

1. Is fitrah obligatory on every individual or is it the duty of the head of the household to pay it on Eid-ul-Adha?

2. If the fitrah wasn't paid on time then what is due on the person?

3. How much is fitrah?