It is disheartening to read about your father's condition. It seems that your father is suffering from a depressive disorder.
You need to consult a Clinical Psychologist who will listen to your father and all his problem and history and then make a diagnosis.
Consult a psychiatrist who works with a Clinical Psychologist, that will resolve the problem. I hope this helps.
Next Steps
Consult a Clinical Psychologist for a detailed evaluation and treatment plan.