Escalation Charges else cancellation of allotment of flat

A builder is Mumbai has included the clause for escalation in the agreement. Since, I read the clause, i have objected to it and refused to sign. Unfortunately the builder has already taken 90% of the payments from me. The project was book in Jan 2010. The permissions was obtained in 2013 and the completion of the project is due in Dec 2017. It appears the builder is trying to make a market correction by charging me the escalation cost. The flat that I had purchased for 27lacs in 2010, after escalation will cost me 41 lacs + 6 lacs for parking. The builder is selling the flats for 49 lacs now in 2016. I have no appreciation of the time for which i have invested in the project as the builder is taking away everything with the agreement. If i refuse to sign, the builder says take ur money back else he will cancel the allotment. 8 yrs with the project are going waste. Can u pls guide what I can do in absence of a registered agreement as the builder is forcing to sign the agreement on his terms.