> 550,000 moderators

You can bring this number down by only reviewing new/low-reputation advertisers, increasing minimum spend, rate limiting, etc.

You can also pre-filter for "definitely not CSAM" and only review the more ambiguous stuff.

I think your numbers are low too, surely a moderator can review over one ad per minute on average. And it may be more effective to split-screen multiple ads (with redundancy).

But at the end of the day it's a numbers game, something is going to slip through.