Landlord deducting very high amount (25%) from deposit for repair

I was a tenant in a flat in Kohinoor City, Kurla, Mumbai till 3 months ago and my security deposit was INR 2 lakhs. I vacated the flat and gave back the flat keys the same day and requested him to re-imburse me my deposit. he has been saying that there was a termite issue in the flat and seepage in the flat because of which he will not be able to re-imburse my money. due to termite issue, he extended the repair work to refurnish the whole kitchen cabinets (INR 20000) and now is also asking me to pay for the painting (INR 30000) Is he correct in demanding this? i have been telling him that termites are an issue in the whole building and this was not something brought upon by me in the flat but he has become very unreasonable and refusing to listen to any reason. if i want to send him a legal notice , how much does that cost and what are the next steps ? i honestly think, he should not charge more than INR 5000 - INR 10000 so want to understand, what is the risk reward in sending him the notice?