Yes, I do believe that it is reasonable to be concerned about the safety of your daughter and your granddaughters. Your daughter reported that she is experiencing verbal abuse. She’s also very fearful of her husband. He has prohibited her from even speaking about his behavior and what goes on in the home.
Additionally, there are other concerning factors. These include the fact that he has a serious mental illness, which because of a health problem cannot be adequately medicated. This means that her husband is actively symptomatic. In addition, he is a “rapid cycler,” psychotic, easily agitated and irritable. He has a history of blackouts. These could be linked to his medical problems, psychosis or to his anger episodes. He also owns guns and has come close to physically harming your daughter. It is possible that he has already physically harmed your daughter but she is reluctant to tell you. Research has shown that family members are often the target in cases where violence occurs. Finally, while he has not physically harmed you, he has vandalized your vehicle. These are all major red flags associated with the potential for violence.
Simply having bipolar disorder does not make an individual more likely to be violent than an individual without bipolar disorder. What primarily increases the risk for violence is an untreated psychotic disorder.
Your next question is what should your daughter do about this situation. That is a difficult question to answer. Below I will list several suggestions.
You said she has a therapist. She should ask for his or her advice. If you believe that your daughter is less than forthcoming about this situation with her therapist, then call him or her and report what you know. The therapist, due to confidentiality laws, cannot reveal information about your daughter’s case to you but there is no law against you providing information to the therapist.
She could also do several other things. You mentioned that her husband is unable to digest or sufficiently consume his medication because of a medical problem. This tells me that he has a psychiatrist or has at least has been in recent contact with mental health professionals. Your daughter could report his behavior to his doctor or treatment team. They may be able to advise your daughter about how to handle this situation.
Other ideas include calling the police or mental health crisis team if his behavior is out of control. If he is actively psychotic and threatening her, he would likely be admitted to a psychiatric hospital. Calling the police or the mental health crisis team can expedite the process of hospital admission.
The safest and most appropriate way to proceed, given the current circumstances, is for your daughter and your grandchildren to move out of the home until his symptoms are under control. Domestic violence shelters can provide a temporary safe house. It is a very volatile situation and your daughter and your grandchildren need to be protected.
My final recommendation is to review the Treatment Advocacy Center website. They provide information to family members dealing with psychiatric crisis situations. They also provide a great deal of other educational information that I believe you and your daughter would find relevant and beneficial.
I hope this helps. Please take care and don’t hesitate to write again if you have additional questions.