Claim on Security Deposit

I own an apartment in Mumbai and a gentleman from Bengal got into a lease agreement with me at the end of February. The agreement was effective from April 1st with a 6-month lock-in period. The tenant in question paid the full security deposit upfront. Because of the country-wide lockdown imposed by the government on March 25, this gentleman could not travel to Mumbai at the end of March as planned. Therefore, he could not take possession and the keys to the apartment are still with me. Moving into the Mumbai apartment also required a meeting with the Housing Society Secretary and this too has not happened because of the lockdown. The said gentleman now does not wish to move to Mumbai anymore and has requested me to refund the security deposit he had paid upfront at the time of signing the agreement. I do not wish to refund the full amount to him and wish to deduct the equivalent of 3 months rent to cover my expenses and effort towards finding another tenant. I have the following questions: (a) Am I on the right side of the law if I deduct a portion of the security deposit before terminating the agreement as requested by this gentleman? (b) As an act of God or natural calamity prevented the commencement of the agreement on April 1st (as he could not take possession at all), has it automatically rendered the agreement void? The agreement we signed does not have a force majeure clause and is subject to the Maharashtra Rent Act 1999. Please advise.