Use of Security Deposit for rent

[Scott LaFountain]

I have been renting a single family house for close to 3 years. Due to being in the military my original written lease was for two years in conjunction with my military orders. I extended onboard at my current command and advised my Landlord that I would like to remain in the house and we verbally agreed upon a month to month lease. At the same time my Landlord advised me that he was raising my rent by $600.00 to a total of $2,400.00 a month. He also advised that my last month's rent would only be $600.00 and he would use the Security Deposit to cover the rest. We both agreed to the terms in which he proposed. Two weeks ago I advised my Landlord that I would be terminating my lease on 31 May 2011 due to receiving military orders to PCS. Today (01 May 2011), when I went to pay my rent in the sum of $600.00, my Landlord advised me that I would need to pay the full rent amount of $2,400.00 because he has a mortage to pay. I know he has financial problems because debt collectors are calling my house which concerns me because I don't know if I will receive my Security Deposit back when I leave. He did not take the rent check when I tried to hand it to him. What course of action can I take or what course of action should I take?