P2 would not harm your chances – in fact the ACA recommend that you take the examinations in numerical sequence
With reference to how much accounting knowledge you require, it is the case that the P7 accounting knowledge requirement is pretty solidly based around just a few of the IASs / IFRSs
Which ones? I suggest that you read the questions and answers from a revision kit – you will very soon recognise the repetitive nature of the questions in the exam
When are you aiming to take P7? Surely not next month!