Help needed to deal with a rogue Chinese tenant

I have a Chinese tenant who is a self-employed home building business owner. Before he moved in, we screened his credit score is 680, and I even gave him 8 days free so he can move in early, I didn't expect he is such an *****! He either hung up on me or shouted at me when I reminded him of the late rent. He's never been on time on rents. Every time when I called him to remind him of the late rent, he always says I am bothering him. Starting this month in December he hasn't paid the rent, and threatened me on the phone that he will move out next month, way before the lease expires in June 2010. At move in I already collected his last month's rent and security deposit. I have a few questions, and really appreciate if anyone can help me out here:

1. I have just mailed him a certified letter asking for written confirmation if he really wants to move out and break the lease early, and asking for the exact move out date. I told him in the letter if I don't get his written move out confirmation, I would still assume he'll stay, and I am planning to give him the 3-day notice to pay rent or quit on Dec 6, five days after due date (I'm in California). Is this reasonable?

2. I guess he won't write any move out confirmation for me, and he will just verbally say he will leave at the end of this month. In this case, I would have to use the last month's rent for December. Is this true?

3. If he isn't willing to write move out notice with detailed move out date, can I assume he will vacate the unit before Jan 1? Can I enter the unit on Jan 1?

4. Can I sue him in small claim court for the unpaid rent which would have been earned after termination until I find the new tenant? Or, is it better to hire a collection agency? Can I sue him for possible damages over the limit of security deposit? Because he uses the living room as storage of his building materials and machines.

5. He has no fixed residence, and he usually lives in the houses he's working on for somebody else. It's very possible I might not be able to find him after he moves out. I only have his SSN, what can I do to recover my losses?

It feels terrible to deal with such an unreasonable guy, I even want to sell this property. Thanks so much for your time to read this, and I really appreciate any help.