I had the same problem with an illegal guest house I rented in LA. The landlord was charging a percentage of the master-meter charges just arbitrarly for each unit, which added up to 115% of their total bill (the owner got free utilities because we paid em for her!)
You should report them to your county Weights & Measures office. They will sometimes do a formal complaint and check your landlord's meters for accuracy. Your local PUC can help too, the actual utility company probably won't step in but you can ask. If your city has a Housing Dept try them too.
I don't think they can evict you for lowering your portion of the bill for what you see fit. First write the landlord a letter demanding to see proof of the monthly bill and to discuss a fair rate for all the other residents. If they refuse then do your own math and pay them what you think is fair market, sometimes they relent anyway.
They may take you to Small Claims court for the unpaid portion but probably not since it sounds like a small amount. If you did end up in court he'd have to prove the charges were accurate, and that you were notified on the lease how those charges were split. If it's not in your lease or in writing signed by you, then don't pay the utilities! It's not a valid charge then.
