Don't worry about extra-curriculars, they will have no direct relevance to your application, imo the only ones which help do so indirectly; things like debating which help with confidence/public speaking/thinking on feet etc. Ignore the Oxbridge book.
As far as the history goes, don't worry about it. I'm not saying it won't affect your application, but it will do probably less than you think. My own experience with A Level history was that it was marked appallingly, with marks awarded seemingly arbitrarily and ridiculous disparities between modules. You should definitely still apply. Excellent GCSEs and AAAB at AS, you will still have a very strong application. Your other A level subjects are all strong ones, in a combination that will go down well with PPE tutors.
Try not to worry about your AS mark, concentrate on doing as well as you can in your A2s, getting a good UCAS application together - try and get something put in your reference about nailing your A2s.
I haven't kept up to date with changes in the UCAS system - do you have to declare module grades? Do you still have to declare ASs? I remember my school didn't 'cash in' ASs, so I didn't even put them on my form. Has it changed?