House owner denying the security deposit

Hi sir, I am ramesh staying in Chennai and rented a house for 9000 rs with a security deposit of 60000. As there is no proper water facility we vacated the house by giving a one month prior notice verbally on July 1st and vacated the house by aug15th as notified. We have paid the rent for the month of july. Now the house owner demands a whole month(August) rent rather than 15 days. And he says that he will give the deposit only if he gets the next tenant. Want to clarify two questions. 1) Does the tentant has the freedom to vacate the house as the basic need is denied in this case, If then does we need to pay full month rent to house owner even though we lived there for only 15 days? 2) As per law how much long can a owner can withhold our deposit?if he can't withhold our deposit for longer time what sort of law suit can we file? 3) We have only an unregistered rental agreement. Is it valid? Can we proceed an legal action with this?