Having reviewed the papers, I would make the following observations:
1. It's interesting to note that extenuating circumstances are not even mentioned in the latest Code of Practice.viewtopic.php?f=35&t=24978
2. This is not to say that the panel cannot take into account any extenuating circumstances (as indeed they appear to have done), but it is likely to mean that the main focus will be on academic evidence of very high ability.
3. It is not possible to challenge the panel's judgement, however strongly we might disagree with it. I'm afraid the only grounds for complaint would be a procedural error so serious as to cause an injustice.
4. The questions you wanted to raise related to the admissions process, so these needed to be dealt with by the school. Even if you had succeeded in contacting the clerk, the correct procedure would have been for her to hand the questions on to the school.
5. Technically the school would seem to have breached para. 2.8 of the Code ("Admission authorities must comply with reasonable requests from parents for information which they need to help them prepare their case for appeal
") by not responding fully to your letter of 13th May.
However, it's not clear to me whether this caused an injustice, because it depends to what extent you were disadvantaged in your preparations for the appeal. (The distance of the last pupil to be admitted in recent years, for example, might be of interest - but it is not strictly relevant to this year's admission round. Moreover, if there was only one pupil on the cut-off score in a particular year, no distance would have been used, because there would have been no need for a tie-breaker.)
6. I'm sorry that I don't understand the issue to do with ranking. I think this is something you probably need to try and talk to the school about.
7. The decision letter is better than most I get to see, and broadly speaking it meets all legal requirements.