A simple utility plugin for changing or deleting post or user meta (custom fields) keys in bulk.
At this point, yes. That may change in the future.
That's OK. Just run the process again with the correct spelling. Remember, if the typo was in the 'new' value, that's now the 'old' value to change.
That is...unfortunate. The process, however, is not reversible. You DID run a backup before, correct?