Is the whole Wacko Jacko thing - the voice, the oxygen tent, Bubbles
etc - just a big PR stunt? Is he far more normal in 'real' life?

Unless you believe the recent trial was a PR stunt, then no, it is his
real life. He really does all the weird things we think he does,
including sleeping with young boys.  As per a juror on the case, they
all believed he did the acts that he was accused of, but the
prosecution did not prove their case beyond a reasonable doubt. 
Remember, he was not found innocent, he was found not guilty.

Obviously I don't believe the recent trial was a PR stunt. What I have
read reports of though is that he doesn't actually speak in that
falsetto voice, he has a baritone voice that he uses to scold
employees. I also read that he supervised the release of photos of him
in an oxygen tent in the 80s as part of a PR stunt. I was trying to
find further information on how much his 'wacko' image is actually a
fabrication controlled by his PR people. I am not referring in any way
to his trial or the accusations surrounding it.

I realise the burden of proof was not met in his trial and that if the
jurors were able to give a verdict of 'not proven' (as in Scottish
law), they probably would have done so.