Applying for divorce

I am a naturalized US citizen. I registered my marriage in India last year to a Sri Lankan physician who is residing and working in India. 1 month after the registration, he and his family gave me the ultimatum of ending the marriage if my family did not provide items of monetary value such as our family home in the US and gold jewelry. I have decided to file for divorce in Chennai as this is where the registration took place. I haven't had any form of communication with him or his family since the incident. I need advice on a few matters 1) We registered the marriage under the Hindu marriage act- he is a Hindu and I am a Christian. Does this marriage still hold valid? No religious ceremonies were conducted; the thaali was not tied. 2) I have proof of their dowry demands via phone messages- will those be considered as evidence in court? 3) As I am a foreigner, will I have to be physically present during the court hearing(s)? 4) How soon can I apply for divorce? Any help in these regards will be much appreciated.