Leaving property before 11 months, landlord is deducting deposit

Hi, I am staying in an apartment that I rented in January 2016. I paid deposit of 10 months and the same was acknowledged in the rental agreement. The agreement was directly with the owner. The agreement says that it will be refunded if house premises is in good condition. The agreement says that tenant has to do the painting work at the time of vacating the house premises, otherwise that will be deducted from the advance amount. The notice period was 2 months in the agreement, but the owner informally assured me at the start that it is 1.5 months or even 30 days. Now after staying for 4 months, I am vacating the apartment and have given him the notice of 1.5 months. When asked for the deposit, the owner now says that he will deduct either 2 months rent (2 x 20000) or 1 months rent (20000) + painting cost (40000). Since he is considerate he will go ahead with 2 months deduction. Even for the painting work, before signing the agreement, he has assured me that painting charge will be minimal if we keep the apartment nicely. We have kept the apartment in very good condition and not put a scratch anywhere. What are the options I have? thanks.