Hello,
You can find info on the Popmart attendance in the For Love Or Money forum. About halfway the first page there is the thread 'U2 Chart/Sales Statistics' which has the figures for all the Popmart shows! Sting did a great job on this one (and luckily his posts are visible again). Unfortunately, there is no info on the capacity of the venue, only of the attendance.
I hope this helps!
C ya!
Marty
P.S. For the capacity of the first few Popmart shows you can look it up in the revised edition of U2 Live: A Concert Documentary.