Landlord flipped on mutual settlement amount from security amount

I am a resident of Ghatkopar west, Mumbai. We have stayed in current flat for 6 months against a lock-in of 12 months. We had transparently asked the owner if we can mutually settle the lock-in period and after few discussions, they communicated to us an amount of Rs. 15,000 plus 5000 incase of any miscellaneous damages, 1 month notice, and we offered to get the whitewash done on our own. We had clearly said that we will start house search only if they are comfortable and our reasons were health-related. We kept our word. But as soon as we finalised other flat, the owner flipped and started to ask for > 1 lac rupees. This episode has caused immense stress to my husband who is recovering from brain stroke. The owner also misbehaved on email/ phone. We also have call records where they agreed to 20k. Had they been upfront about their ask, we would have completed the lock-in. What has hurt us is the opportunistic flip. They have been very non-cooperative even with essential repairs (broken floor tiles which is a safety hazard). I feel helpless about this blackmailing and I sincerely hope a fair closure. Please guide me.