Ask a landlord-tenant lawyer and get answers ASAP
Thank you for your question. I look forward to working with you to provide you the information you are seeking for educational purposes only.
Under CA law, the lease guarantees you peaceable use and possession of a habitable premises, which they are in breach of. If the premises is not habitable, they are liable to forgive any rent or pay for you to stay elsewhere until they fix the problem. So they are in breach of the lease and you have grounds to sue to recover ALL of your money, PLUS the money you paid to stay elsewhere.
Furthermore, this situation sounds like an illegal rental and it is grounds for you to file a complaint with the local housing authority as well as the local building inspector and health department for the bugs.In addition, in suing the landlord for breach of lease, the fact they offered you one unit and gave you something else is an unfair and deceptive business practice under law and it would entitle you to sue for up to THREE TIMES your actual damages, plus attorney's fees.
So I would suggest you get a local attorney and sue the landlord for breach of your lease as well as unfair and deceptive business practices and file your complaints with housing authority and building inspectors and get out of this situation as soon as possible.