Sum of multiple Index/Match results using array formula

[cray36]

Hello,
I have a sheet that I set up to calculate event participation among attendees based on a target number of points that is required of them. It calculates the percentage above/below the target that their accumulated points came out to be. My goal is to take those percentages and average them based off how many events they attended. If you see the attached file, it should explain a bit better.

Since i'm going to be continuing to add event data, and the dates they occur on change, I tried to use the following formula as an array formula

=SUM(IFERROR(INDEX(6:8,3,MATCH(E$1,6:6,0)),0))

That formula is currently in E:3, and it shows the sum of the event percentage earned by Person A during Event 1. But I can't figure out how to set it up as an array formula to do an Index/Match to find every instance that "A" appeared within E6:AH31, and then sum the participation percentages, in a single cell.

If you see the yellow cells and below, that's if I copy down the above formula, and it works like a charm to find the percentages I want, and the green line is the actual number i'm looking for which is the sum of all the non-errored results it finds. But I need to do it in a single formula.

Any Ideas?