Cancellation of flat booking..

Hi, I was booked a flat on 25/03/2017. After that due to RERA and GST things builder post pond the things and last week he came up with the draft agreement with some clauses with which I am not satisfied. So I have decided to not go with that agreement and asked builder to cancel my booking but then he told me if you want cancel the booking you need to pay 50000k against cancellation as administration charges. Please note here on booking form he mentioned under terms and conditions that 50k will be charged against cancellation on booking. But if we consider booking form then lot of things are not correct in the booking form..let's take an example - Agreement value - 3614520rs Service tax (3.09) - 162653rs (as mentioned in booking form) but if you actually calculate with 3.09% it will comes - 1,11,689rs Stamp duty & Registered (6%)- 246871rs (as mentioned in booking form) but actually it comes - 2,16,871rs Also on booking form builder mentioned area as 917sqft (85.22sqm) but on draft he mentioned 605 sqft carpet + 117terrace area = 722sqft (67.10sqm) Also he is asking 10000k as legal charges in cash...etc Because of all this I took decision to cancel the booking. Can I accept 50000k cancellation charges? Or should I claim 100% refund? What is the legal process for refund so that if needs i can go to consumer forum ? Thanks in advance!! Regards, Manoj