A few clarifications on rule 3
>Do we report actual posts containing text referring to sexualized underage characters as well?
If it's clear or heavily implied within the text that the character in question is underage, yes. If there's no mention or implication of age at all, don't worry about it.
>The new rule seems to include pretty much any media and anything that looks under 18
This is always the most frustrating thing about rules like this, but going by the precedent set by most other sites that have experienced something similar, it's based on how the character looks, yes. For example, characters like Yoko Littner from TTGL would likely be fine, as even though she's technically referred to as 16 years old within the story, she looks to be of age. Meanwhile, 1000-year old loli dragons are a no go. Assume we're working on body type, both for images and descriptions.
>What about offsite links?
Direct links to images are banned as well, but otherwise links to other sites that may just happen to have said images are fine.
>Cropped, non explicit images of content that would break the rule(ex. closeup crop of loli ahegao)?
Context would be important. Is it clearly a minor/loli character in a compromising position, even with it cropped? That would have to be deleted. Does the crop leave just a smug looking anime girl? Then it should be fine. If you're unsure, report any potentially offending images anyway and I'll make the call. There won't be bans for images that accidentally toe the line, nor for being a bit overzealous in reporting.