Builder not returning money post cancellation since 2 years

I had booked flat in Dec-2012 at Samruddhi Sunshine project – Bangalore . Due to personal reasons I had to cancel the booking in March 2014. I had promptly made payments as per the timelines in the agreement until cancellation. Upon carefully scrutinizing the sale and construction agreement signed, we found the below two clauses worth mentioning -- Cancellation clause: It is categorically agreed between the parties to this agreement that this agreement is irrevocable and in case of the second party/purchaser defaulting the payments in the manner stipulated here under or in the event of the purchaser rescinding this agreement either due to nonperformance or due to the breach of the terms and conditions, the first party in their discretion shall refund to the purchaser such sums of money received from him without interest however after deducting the expenses from the apartment cost towards liquidated damages apart from recovering the expenses incurred for re conveyance of the said apartment to third parties. Arbitration clause: The parties agree that in case of any dispute arising in respect of this agreement the matter shall be referred to arbitration of an arbitrator in consonance with the provisions of the Indian Arbitration and Conciliation Act 1996. the sole arbitrator shall be appointed by the second party and the decision of such arbitrator shall be final and binding upon the parties hereto. After almost 2 years we were told that the builder has confirmed via mail that a prospective buyer has been found and refunded 50% of my money back. For the balance 50%, we have been asked for an indefinite wait without any timelines and also told(by the builder) that they would file a criminal case for cancellation against us if we are taking a legal route. Now all of a sudden there is no response from them and we are being threatened that repeated requests might lead to cancellation of agreement with the new buyer and an indefinite wait again ! My doubts are: 1. Does the cancellation clause mean that we will be refunded only after the builder finds a prospective buyer for our flat? Cant the builder provide the amount from his firm and not wait until the prospective client pays him ? Can the above cancellation clause be challenged in court . 2. Does this clause mean that the builder can decide on the amount he can deduct as penalty? if so then can it be any percentage of amount? Also since we have been given 50% of money post 2 years, can I claim interest and harassment charges against the builder. 3. Does this clause in any sense state that there is no time limit for refund? 4. Does the arbitration clause mean that we cant approach the consumer court? or any court for that matter? 5. What is the weightage that my case has when approaching a court – If so which court should I approach. 6. Please suggest next steps .