I have still not got the hang of the question. If I understand correctly, the girls father is asking for 10 lakhs and threatening to file a case of dowry demand otherwise.
In such case the only recourse which the father of the girl is to file a case under Section 4 of Dowry Prohibtion Act, 1961, which entails a maximum punishment of upto 2 years.
The said offence is bailable. So there is no threat of being arrested in the said offence.
In the instant case, you can record the demands of your would-have-been FIL and file a case of extortion against him.
He has at a very disadvantageous position but still able to subdue you. The scenario is worrisome and shows how frightened we become at the very mention of any law related to dowry.