Deposit not returned by the owner

We rented a flat in SEP-2017 with 14k as rent and 40k as deposit. In around FEB or MAR-2018, a construction site for flats was set up right next to our house...Our house was completely darkened as they put tarpolene sheets and there was continuous sounds due to the construction. There was cement everywhere and i started having breathing and health issues due to that. We decided to shift and started searching for a gated community in our budget (as my husband and I have just started our careers and do not have much of savings). We found a flat for 15k and around 10-AUG-2018, called the owner and told that we would be vacating due to health issues and asked him how to give the written notice. The owner said since its health issue, no need of any written notice and we could shift at the end of AUG-2018 which he had no problem. We thought he was really sweet and agreed. now he is refusing to return the security deposit. We did not pay AUG-2018's rent and told him to deduct from deposit. As per the rental agreement, at the time of vacation, one month's rent for painting and cleaning would be deducted. so 14 plus 14 should be deducted and 12k shd be returned back. But the owner wants to deduct 02 month's rent 28k plus painting charges 8k which totals to 36k and says would give back 4k. When we asked him, he says we did not tell him in 02 month's advance and no one has come yet to that house, so he wants to collect money from us. He also says that we did not give anything in writing. All i have now is rental agreement which says one month's rent would be deducted and online payments done to him. Could anyone plz guide what to do next? Is it possible to file a case in consumer forum online? if yes, what exactly is the procedure and how much would it cost us, both in time and money?