In a dangerous situation like this, it is recommended you call Adult Protective Services and talk to a social worker there about your rights. They intervene when someone is a danger to themselves or other people and it sounds as if your loved one is both a danger to themselves and to other people.
Regarding refusing to stop driving, if taking away the keys isn’t working, you may also need to disable the car so that your loved one can’t drive. You can talk to a mechanic about how to do this.
In addition it is recommended you attend a support group through your local Alzheimer’s Association chapter. The other participants and the leader can offer you practical suggestions about how to deal with this situation.
Please don’t give up! This situation sounds like it has the potential to be unsafe and therefore help is really needed. Therefore, it is critical to contact Adult Protective Services immediately.