My question involves landlord-tenant law in the State of: San Diego, California

I have searched the internet and have found conflicting answers to my question, so any help is much appreciated!

I am living in a 3br home with two roommates. I was added to the roommates' existing month-to-month agreement via addendum, which took one previous tenant off upon adding my name. Upon moving in, the landlord insisted that even when I gave 30 days notice to move out, and even if I moved out by the end of that 30 days, I would still be responsible for rent until I found a person to take over my spot on the rental agreement. I should add that my two roommates will be staying in the house even though I will be leaving.

Our agreement specifies that "Tenant may terminate the tenancy by giving written notice of at least 30 days prior to the intended termination date."

After looking over our agreement further, there is a clause that says:
JOINT AND INDIVIDUAL OBLIGATIONS: If there is more than one Tenant, each one shall be individually and completely responsible for the performance of all obligations of Tenant under this agreement, jointly with every other Tenant, and individually, whether or not in possession.

Me being responsible for rent after the 30 days seems absurd, since I could hypothetically be responsible for my portion of the rent indefinitely if I can't find someone else to replace me. Of course I will make every effort to do the right thing and help my roommates find a new roommate, but I want to know what, exactly, I will be legally responsible for paying when I give 30 days notice and vacate. So my questions are:

1. Am I responsible for ANY rent after I give 30 days notice and vacate the premises if we can't find a new roommate?
2. What happens to my security deposit if I give 30 days notice and vacate, but can't find a new roommate to take my place?

Thanks very much!