Crazy tenant goes nuts, does damage ...but moves out voluntarily?

I had a room in my home that I rented under a 6 month lease to a 30 year old man with his mother as a co-signor. He paid 700.00 in rent each month plus an equal share of the utilities and had a 600.00 deposit. The tenant paid rent on July 1st, 2009 and at 3am on July 3rd, 2009, he flipped out on alcohol breaking dishes and kicking the walls in his rented room. The police were called and beat on his door but he played possum and did not respond...so they left.

Today, I confronted his mother on the phone and him in person and told them both that he needed to move out immediately as we were afraid of him. They resisted it initially but after several minutes of reasoning they both agreed and he packed up his belongings and left. Everything was fine until he had everything packed into his mother's car. Then he started swearing at me and my wife and threatening us physically. It ended with him refusing to return the keys because he wanted his rent and deposit refunded.

I calmly pointed out that his violating the terms of the lease and voluntarily leaving, although at my verbal request, occured as a result of his own behavior and that I would not suffer the loss of rent as a result of his deliberate and wrongful behavior. I pointed out that we still have a lease in place and I am entitled to collect rent until I find another tenant. As he was not evicted, but left of his own accord...I feel I have no obligation to refund his rent or account for his deposit until I:

I find a tenant to take his place.

Make the necessary repairs to the room and have a invoice for him for the damages

Invoice him for the outstanding utilities.

He left amid a storm of cursing and threats...but they did eventually leave.

In an effort to mitigate my damages, I have run another ad online and solicited ten people posting in search of a rental room on Craigslist which is where I find tenants...and how I found him. The room is empty and he still posseses the keys. I will change the locks tomorrow and the costs for that will also be part of his final statement.

I did not force him to drink, do damage and act in a threatening and scary manner...so I feel that I should not suffer the 700.00 rental loss. He left without any legal notices so he did so voluntarily after being told that I would not be refunding any rent until I had a new tenant in place...and then only if it happened prior to the end of July...in the correct, pro-rated amount.

My handyman has given an estimate of 400.00 to repair and paint the room and the private bathroom and to repair a door frame he broke while drunk. The locks will cost an additional 100.00 (45.00 for the hardware and 55.00 for labor). His share of the utilities are usually 110.00/month...so I am already at 610.00 on a deposit of 600.00.

I have told him to be patient and that as soon as I rent the room...he will get a pro-rated portion of the rent back provided I can get another tenant before the 1st of August.

I also advised him that should the room not rent out, he and his mother would be responsible for the August rent as it is the final month left on the 6 month lease.

I intend to detail all of this in a statement and to provide him with the receipts and/or a handyman invoice within 14 days as required under California law if he will provide me with an address to send the statement to. He is currently refusing to give me a new address and now calls continuously threatening legal action.

While I am aware that anyone can sue for any reason...I want to know if I am doing anything improper? Please advise