It's not specific to class, but all of the sounds you're describing drive me mad to the point of anger, tears, and having to leave the room. At uni I avoided entire lectures because I knew there would be people eating, biting their fingernails, chewing gum, or whatever.

You could look up something called 'ear guards'. They're designed for people with autism who are seriously sensitive to noise. You could also try earplugs, sometimes they will block sound just enough to help but not enough that you can't hear speech. And if you're flush with cash, noise-cancelling headphones are AMAZING. You'd have to tell your lecturers why you're wearing headphones in class, though.