Hello there. So sorry to hear of the difficulties that you and your family are going through. From the description it is evident that your father is having a psychotic disorder, possibly delusional disorder. Fortunately there is treatment for this. Kindly reach out to a psychiatrist and they will do a detailed assessment following which appropriate treatment can be given. It is also possible that your father may not consent for a consultation. In such a scenario your mother and yourself can make an appointment to meet the psychiatrist as there are options for such a scenario too. Wishing your family the best.
Next Steps
Please reach out to your psychiatrist and explain your difficulty. Your doctor will do the needful.
Health Tips
Perhaps it is possible that your father may not be willing to visit a psychiatrist. Do not get disheartened. It would help even if you and your mother visit alone and provide a detailed history following which your doctor would be able to offer an appropriate advice.