You weren't supposed to be reading!
However, my mistake was putting up with the statistical grilling for too long. It was an area the examiners knew well, so they enjoyed talking about it. I didn't. I should have deployed my "not a stats thesis" argument earlier. Now you have the same argument ready!
It was also partly my fault for suggesting an examiner who was so statistically orientated - I should have known the second one (who I didn't get to suggest) would be too! They were both very well-known and respected ornithologists too, but neither knew anything about the applied, toxicological aspects of things. Can't blame them for sticking to what they knew, I suppose.
Like you, though, I was really at the point of not caring whether I got the damn thing or not, and that was a coping strategy in itself. It's very rare for anyone to fail a PhD once they have got to the stage of submitting a thesis and the thesis has been through a revisions stage.
To fail at the viva, the thesis would have to be pretty weak. If the thesis were weak, your supervisors would tell you.
So a viva seems to be a sort of initiation rite which may not be strictly necessary but continues anyway.
I have been improving the English of a number of papers and theses for some of my german oppos. Two of them have been through vivas (one in English!) and said afterwards that they enjoyed them. So don't let my unfortunate experiences scare you too much!