Your best course of action is to tell your police agency what you told us, and have them take the steps towards giving Google a subpoena for the footage from yo

Your best course of action is to tell your police agency what you told us, and have them take the steps towards giving Google a subpoena for the footage from your account for the period requested. That subpoena will make Google liable if they fail to deliver it prior to its deletion, and make this no longer your problem.