Delay penalty charges

I bought a flat in 2011 in amrapali, noida extension and paid around 40% that is 12 lacs of the payment. till now complete structure of the building is ready but finishing/pop and other work is on hold. they kept demanding the balance money but i did not gave them any money after 2013 december as they were supposed to give the possession in 2014 but since the work was delayed, it seemed that the possession will be given in 2016..also i received a pre cancellation letter from them in 2014 that my unit will be cancelled if i did not paid the balance amount in 15 days and amrapali is free to sell the same to any other client and i may collect the amount paid after cancellation. on calling the amrapali guys, they told me its just a procedure and no cancellation will be done and but there can be delay charges around couple of lacs. currently since im not in a position to pay, im trying to sell the same at 2300/-sqft at which i bought while the current cost is 3200/-sqft, they have levied a delay discount of 6,20,000/-..half of what have i paid.. im so pressurized mentally that do not understand what to do here.. please guide..