For some reason, I can't seem to change anything in single player, or when I create a server, things like the current mod (I want to use classic on multiplayer without DQs, among other things). I've tried looking up the admin commands, but nothing seems to work... Any help?

Try to use admin commands on single player.
eg. /set ed 500 to change engage distance.

The servers seem to be broken now, you can't change anything cuz u don't get @.

ahh crap im having the same problems!

Try and make the server, then press Escape, go to Game rules, and change the settings, they will apply in multiplayer.