Our Contractor did not complete the building within given time and now he asking for extra @15%

Our flat Supposed to deliver within 26th months with CC & OC, but our contractor has already failed to deliver the building within the time period while we have paid the entire money as per the agreement and additional 1 year has already passed. Now he is demanding extra @15% of the cost of constriction otherwise he will not continue the work, which has no meaning as he has delayed the project by 1 year intentionally with lame excuses. The contractor intentionally did nothing, he left all the works half-done always and asked for next scheduled payment and said he will not complete the current work if we don’t pay money again and pressured us several times. He gave us another new schedule again with the full paid certificate for the same works with additional money before. He has already stopped the construction work before the new restrictions of COVID-19. Out of 8 owners most of them are retired and we all belongs to the middle class families, we have taken loan from bank and paying EMI since 2018 and some of us has given money from their retirement savings. Now it is impossible for us to arrange this extra money because now we have nothing left in our hand after paying the full amount. We went to PS and talk to the officer but there the contractor told us that we have to pay at least 10% of the cost of constriction otherwise he will not work. The PS told us to either file a case or go for settlement. The officer of PS called us again, he also called the contractor for final settlement. The contractor delayed the all works from the beginning and as per the work we gave him payment now he is giving us false allegations that we made the delay payment that is why he is doing this. He never completed the works on time. He took almost 4.8 lakhs in January 2021 and told us all the tiles works of bathroom, kitchen and stairs will be completed within 15-30 days but till date he has completed only 6 common + 6 attached bathrooms, this is how he is working from the beginning. He gave us the new agreement draft copy with 10% increased rate, we took time to read and discuss and again he has sent us a letter today saying that we took long time so he will not work as per the sent agreement i.e. @10%, he will increase the rate more than 10% again. he is continuously pressuring us. We are in a false position sir, please help us. He is cheating on us again and again. What to do?