Rescinding a MOU signed for sale of a property

Hello, Recently I signed a Memorandum of Understanding to sell my property in Bangalore. The MOU had 3 clauses 1. The buyer would pay an advance of x amount on signing the sale agreement. 2. A second advance of x amount would be paid at the end of the month the agreement was signed. 3. Final payment of remaining balance would be paid in three months from the date of the agreement. After signing the MOU, I found the buyer yelling and being disrespectful to my agent who arranged this deal. I found buyer yelling, verbally disrespectful and agitated saying the deal did not meet his expectations. On my objection buyer said he would see to it that I will not be able to sell the property to anyone else and stall any other buyer to buy my property. Next day the buyer called me to sign the sale agreement which I refused. The buyer is demanding an exorbitant amount (about 20% of the sale price) to cancel the MOU and threatening with legal actions if I refuse to complete the deal. Here are my questions: 1. As a seller what are my options to have this MOU cancelled since there was no advance was received on signing the MOU. 2. I now have a buyer who has agreed to purchase the property and settle the deal in a month's time. I am concerned that the first buyer may cause unnecessary problems to complete the deal with the second buyer. Is there a way for me to prevent the first buyer from causing any further trouble in completing the deal with the second buyer. Please help me with your advice.