Underconstruction Property - Construction stopped by builder

I purchased a flat in Greater Noida west under newly launched project in 2012. Now builder keep on launching new towers in this project but almost stopped construction on Phase 1 towers after 1st floor (30+ floors & 45+ tower project, 20+ under Phase 1). I paid 6 installments on time which is almost 45% of the cost till now under CLP. Last year I stopped last installment as builder is asking for it without having any visible progress in construction. BBA is already signed at the time of 2 installment with standard clause that in case of non payment builder will charge 18% interest & have right to forfeit flat & 10% of flat value. Now as builder is delaying the construction & is not able to fulfill the commitment on time, I want my money back by surrendering the flat back. As per one of the BBA clause, we cannot transfer the ownership unless 80% of payment made in regard to cost of flat, so transferring a flat ownership is out of question. How can I be assure to get my money back without paying 18% interest on nonpaid installment & also without paying 10% of cost of flat as penalty. Can tell the Builder & Project details if in case advice is builder specific. Recently celebrity endorsing this builder walked out of the contract due to controversies. Ragards, Vivek