Do consult  a Psychiatrist for the medications and I  would suggest  that visit a Psychologist  too for counselling  sessions so that he maybe able to express his experiences and some other feelings  which may be case of his behaviour. They will also help him to come put of that behaviour and lead a healthy life.

As you have rightly noticed the lack of sleep is one of the major outcomes of ongoing stress or disturbance in either body or mind. Stress he is going through is being expressed as short temper & tension. It's awesome that you are opting for long term solution rather than going ahead with pills. Please consult a psychologist or a psychiatrist for detailed evaluation and counseling so that he/she may help your father understand, embrace and overcome the difficulties which are bothering him & depriving him of sleep( a natural state of calm & peacefulness). This is a process which would go in it's own pace & the professional will help him to eventually reduce the dependency on pills. Good Luck.