Sec Deposit and balance rent

This is in Califonia

Would like to know about the requirement of a 30-day notice IN WRITING in a situation where one rents a room and the landlord also resides in the same unit.

I informed my landlord 30-days in advance regarding my intention to move out in 30-days. He started showing the room within a week. I moved out in the middle of the following month, As he held my last month's rent i had the remaining half months rent with him. I asked him for it when i moved out but he refused to talk about it. I sent him reminders by email but he has not responded.

1) Can he refuse to give me back the half month rent as i did not give him a notice in writing?
2) I would be taking him to the small claims court anyway because he has not given me the back the deposit after 21 days. Under what circumstances does the court normally impose a bad faith penalty for not giving back the deposit?

Small Claims Court is the right place. I don't know about the rules in your state but usually there is no penalty absent some state law imposing one.