Have been cheater by contractor

This is a Civil case. I had given a contract to a contractor for building an house on my own land. The whole construction was worth Rs 10 lakhs. An agreement had been signed. I have already given 7 lakhs to the contractor but he has only completed 1/2 the work. The quality of his construction was very bad and pathetic. So we asked him to stop work. We filed a Police complaint as the contractor said the work is worth the money. The contractor sent us a court notice a week later stating that we owe him Rs 50000 because construction cost up till now has been Rs 7.5 lakhs. We appointed 2-3 Govt engineers who gave us a written estimate that the construction is not even worth Rs 4 Lakhs. Police to tried to get hold of him but once civil case was filed they said they wont be able to help us since its in court now. We tried to confront him for an out of court settlement, but he said that let the case be in court for 50 years. Even if its fast tracked, he said he will tell the court that he is broke or give a yellow notice or even pay only Rs 100 per month. He even went to an extent to say that he will get a stay order on the property so we cannot do any construction. Please advice. I have already spent a lot of money on lawyers.