Welcome to WebmasterWorld Guest from 126.96.36.199
b) if content is user generated then it has to be checked against all the bad things
Google do not appear to want you to systemically police ALL user generated content. I have user generated content and must be breaking the T&C in a hundred places.
What I do is use "best endeavours" I publich my own T&C and ban/remove bad content as it is reported or found by some autoscanning code I use.
As ever I think google can tell the difference between an expected level of issues with this setup and systemic abuse.