Some expert whose name I can't recall (sorry) said NAC was probably safe to take between 200-500mg daily. So more than 600 seems high unless you've had a noise trauma I guess and then could take a higher dose only for a while, but I'm no expert. I take 300-600mg but often skip days and a day or two at 1200 if I know I have some noisey situations coming up like travelling. And take with vit c as that article says.
I believe it takes your liver around 9 days to convert it into glutathione.
I wouldn't take it after alcohol. One study reported NAC can protect the liver from alcohol damage but only if taken prior. They found taking it after actually increased damage.