You are not addressing your claim of ad populum in context. Let me help you think through the issue. It is indeed true that we cannot cite number of adherent or percentage of adherents in a sub group as fact, however:
1) Most people are rational
2) When 90% of people agree on a fact, usually these 90% are correct
3) When 10% of people agree on a fact, usually this minority is incorrect
4) Every culture in history has been religious and 90% of all people, ever, have expressed a belief in the divine
You are saying "ad populum" as your mantra (I say that because you feel it's "winning" to do so on four or five of my posts daily) without acknowledging that in this case (God exists) you are claiming that most people who have lived are not rational.
If you accept my #1 above, kindly deal with 2-4 above, instead of telling me I don't know what an ad populum is. Of course I know what it is and also that you're guilty of ad populum (most atheists agree, there is no evidence for God).