I was trying to think of your solution first.  Then I realized that through my work career that when my bosses were really totally irrational and crazy that there is no real solution directly with them as personalities.  It's like someone with road rage.  I had a job as a legal secretary while in NY Manhattan for an entertainment law firm.  One of the main partners really had serious problems.  I went to his office once to get his signature on something and as I recall for no reason he went wild and began throwing papers off his desk and yelling.  I knew nothing I ever did was my fault around this guy.  He did need medication as it turns out in gossiping with other people who had been there longer and was known to have these emotional outbursts.  When younger I used to wait about 6 months on a job and then decide when I'd had enough and then just begin screaming at the person when they came at me the wrong way and told them everything I thought was wrong with them; sometimes even swearing directly.  I never got fired which was odd.  But the lesson in terms of dealing with bosses was that the few times I tried this hoping it would leave a lasting impression, once again I found that the person didn't even hear me and went on acting exactly the way that drove me crazy no matter what.  The point being I've tried open yelling and swearing and it had no lasting effect.

I never did have the maturity to do what you have stated which is to appear busy in order to avoid the person.  Mainly, I was usually able to have my desk put where I was far enough away that the person wouldn't see me very often.  Rather than appear at all, let alone appear busy.

I know that on temporary jobs with an awful boss who gave me no work to do, I was yelled at for trying to read a book to pass the time.  So I became very careful about that and would just sit and reflect.  I guess all I can say is that if the boss is really bad to you, I believe they need both medication and therapy and if they have a superior you can talk to them in your most charming manner and suggest that the awful boss be given some retraining type of help which might even suggest that they need mental health care treatment.  The real problem is that such people are not only sadistic, they are really mentally ill and need treatment desperately and have probably never been told so by anyone who could get them to it.

As to keeping busy, I'll have to think further on that one to see if I can think of anything really creative, as I am trying myself to move from ordinary journal type writing to more creative writing and want to do at least an online class if I can in this area.  It's good I chose your question, as there are web sites on the side here for writers!

Best of luck.  I worked for 17 years at a variety of office jobs in San Francisco and Manhattan NY and I did have a great range of off the wall bosses.  Nothing every really helped and I think getting them off your back is the answer.  I used to at my first job apply for any new opening in a different department as soon as I saw something better as well.  That worked great - I found some of my best job assignments that way.

If something very brilliant occurs to me, I'll write again another answer.