As far as I know, you can't remove them from your Steam account -- I've never heard of Steam removing Achievement, so...
You won't get banned for using the Console to add Achievements, because in Skyrim they're literally right-there in the accessible code of the game (via the CK); heck, I'm pretty sure I've gained a few Achievement from messing with Mods and circumventing quests, so... Nothing bad has happened to me
You will probably need to start a new game, though... Or reload an earlier save (won't remove the Achievements, but I *think* right now your game is going to be pretty boring :/ )
How does one "accidentally" type "caqs" into one's console? Is it a "million-monkeys-with-typewriters" kind of random thing?