So, I took him aside, and I got all creepy quiet, I got the crazy eyes going, and I said, "You stay away from Lily, or I swear to God I'll eat that moustache right off of your ugly French face."
What does mean "going" in this sentence? I think it's not a formal expression..
Also, if I say "right off your ugly French face" would it be awkward? I think there is already the preposition "off", so I think "of" is needless...
That's right - it means that the person used body language (crazy eyes) to intimidate / warn off. This would emphasise the words used. When the body language matches the words then the impact is much stronger and more believable.