Using deposit for last month's rent

[Chynna]

We have lived in our rental for over 2 1/2 years. When we moved in the landlord and his wife had just bought a new house and vacated this one after living here for 27 years. I did not realize how filthy it was until we started putting stuff away. I did a ton of cleaning in this house just to be able to live in it without getting creeped out over the filth. We have always paid our rent, have taken wonderful care of the home and have even spent hundreds of dollars to make a nice yard that all the neighbors have complimented us on. I do not get along with the landlord's wife... she has been really hard to deal with. They also wouldn't clean their belongings out of the extra garage (included in the lease) for 6 months... making it so I had to park my brand new car outside so I could use my car's garage for storage. Needless to say this almost landed them in court.

Situation is this. We have purchased a new home and will close on it the 15th of August. I am thinking about sending the landlord part of August's rent... and telling him to use the $500 we gave him for a deposit for the rest of it. There is no way they could claim any damage to this house after all the work we have put into it. We've even been told by a realtor that we have increased the value of this house. Knowing his wife... I feel it will be very difficult to get our deposit back. I of course will supply him with 30 days written notice that we intend to vacate the property on August 31st.

What are your opinions of this?