All the other races in the series except the one the redress is for. Discards atr not applied. 

'All the races' would be all 9 races in your example.  You can't figure out which scores are to be discarded until you know the score for each race including the score for the race in which redress is given.  You may also need to know that score to apply tie breaking procedures, see A8.2 and consider that the race redress was applied to was race 10.

You can also easily construct a series of races scores where it makes a difference.  For example, consider races scores of 1,1,1,10,10,10,15,18,100 for races 1 through 9.  Race 10 is one for which redress is given.  If you do the discards first then the average score is 6.9 for a total of 54.9.  If you don't do the discards first then the average is 18.4, the redressed score is one of the discards, and the total score is 66.  This could easily change the final rankings and change tie breaking results.

AS PRO for an international regatta, I screwed over a team by applying a discarded race to this math. I regretted it but felt bound.  It might be best to get the protest committee to specify that the score is the average of the other races not discarded for that regatta, if that is the more desirable result.

I still feel bad about that result a decade ago.

Michael - you can stop beating yourself up.  Redress is what is supposed to be *fairest for all* boats, not just the one you are giving redress to.  Average points is supposed to represent the performance of that boat over the entirety of the series not just their best races.  If you apply discards first, you are skewing the result towards the good end of the scale.  Also, if the boat felt you did it wrong, they should have asked for redress and the PC would have sorted it out.

To modify the original question

I’m thinking a series of 15 races spread throughout the year and geographically, with best 5 to count.  

And it is not a hypothetical question, has happened and affected the overall series winner, though some time ago now.  The words ‘average points’ were not interpreted by the race committee in the way intended by the redress committee, so one learning point was for the redress committee to say exactly how it expected the average points to be determined.  

You ask too much.
In a long series I still think you should count all races, the only consideration I would have is if there were a minimum number to qualify. 
The pc at the time has to consider this and weighting. It is initially up to the party asking for redress to say what they want. If they do not ask correctly they may not get what thet think. 
The responsibility is not fully on the pc, the competitor directs.