Dear Rob,
I don't want to get into the illness issues, but I have some other questions for you.
You say your Dad owns the Company - is there a board of advisers or any kind of management reference group? If so, can they help you to stand up to your Dad about his behaviour?
I know it is not ethical to do this, but could you video (perhaps on a mobile phone?) one of his tantrums and confront him with it?? You could say something like: "Dad, these are not the actions of a rational, healthy man. I am convinced you are not well. Let us look into this further" - or something similar. Sometimes drastic situations require drastic measures.
As far as your Dad's staff are concerned, I think you might need to get them on side by explaining you are doing everything you can to get your Dad the medical help he needs.
In Australia, the staff could complain to WorkCover (OHS body) that they are not safe in their workplace, because a safe work place includes both physical and psychological safety. Obviously your Dad's levels of abuse create an unsafe work place psychologically for some (if not all) of his workers. WorkCover would then act to ensure their safety.
Are your workers in a Union? Perhaps they need to be encouraged to seek union action??
I realise this all seems incredibly harsh, because it is your Dad and I'm sure you love him. The trouble is, he won't have a company for much longer if he keeps going the way he is. I'm surprised he hasn't had mass resignations already.
I am presuming you are his "heir apparent" for the business, so I am afraid it needs to come back down to you in many ways. If police are called and your Dad is a picture of calm and rationality, TELL the police yourself that this was not the case a little while ago. Your word about your Dad will probably be taken more seriously than other workers.
I realise I am suggesting you stand up to your Dad and I know this is an awful thing to have to do, but it does sound as if he is out of control (for whatever reason) and really should step down from the company. If he goes too far one day and injures a worker physically, he may face jail time for it!!
Please know that despite my apparently hard hearted attitude, I am desperately sorry for you and for your Dad. The only other thing I can suggest is that you start encouraging him (if you aren't already!
) to "retire at 70". You could talk about the big retirement party as if it was a given, etc. and see if he is even vaguely receptive to the idea?? Whatever happens, please let us know how you get on.
Thinking of you and sending you best wishes for strength to cope with this very difficult situation.