Clarification needed on ending tenancy

Possession - Section 8 and Section 21

Hi, I am serving notice on a tenant to leave, preferably a Section 21 due to rent arrears, aggressive behaviour, and I caught him smoking dope in the garage last week.

My questions are:
1. Can I serve a Section 21 if there is no deposit? (he has rented a room from me for 3 years and has never paid a deposit). However, he did sign a new AST in February)
2. Can I give him a month's notice and serve the Section 21 now or do I have to wait until his AST expires on 24.8.13? and serve the Section 21 8 weeks prior (mid-June)
3. I am going to submit a CCJ for the rent arrears. Since he didn't pay a deposit, if he trashes the room can I claim any "making good" expenses from him, and add them to the CCJ?
4. If I have to wait 8 weeks for him to leave and he stops paying rent, can I add the further rent arrears to the CCJ claim?

Thanks for your help!