I identified the flaw in your numbers, formulated the fix, did the research and posted the results in about 2 min. That seems pretty impressive
Two minutes for you is impressive. All the ladies say say. Well, it's in the personal section of CL, anyway, they could be ladies. Plus, I took care of my own problem before you came around. ;)
The only reasonable way to extrapolate would to be do it by country stats. Number of cases per 1000 of child sexual abuse in a given country then reduced it out to the same ratio per 1000 of jw in the same country.
I don't think that would works to get us close (but, so far the closest). The reason for that is that insular, secretive religions tend to have serial molesters with victims at the ready, often in a position of authority and friends in power ready to defend him, something an offender in the general population doesn't generally have.
It's a better number than we have now, but the problem is that this has been hidden for so long, distorted, records destroyed, etc., with all of these churches, that we've no real way to estimate what the number may be because of this and a variety of other reasons.
We need the LIST!