Call the health department, the building department and/or the rent control board in Los Angeles to see if they can help you. As for the landlord responding to every one of your demands, he does not necessarily have to.
If you are concerned about possible health issues, you should find a new place to live.
Contact an attorney right away - this is a landlord/tenant issue and you may be justified in withholding rent - however, do not do this on your own. You need to be advised by an attorney!
This is my opinion and should not be construed as legal advise for your specific case as there are many more facts which you have not provided.