He definitely still has his job. He wasn't skewered by the national media. He's gotten messages of support from his fans. Most people (including you) are demonizing the woman and not blaming him for anything, not even bad judgement or being a horn dog.
But apparently you have some inside information that I am lacking since you are so sure that his life has been ruined.
For some reason you seem to be taking this all a bit personally and you are out for blood. You want that woman to pay for what she did, goddamit even though she hasn't seem to have done much as pretty much no one believes her story or took her very seriously. You aren't looking at it logically since you can't even say what she should be sued for just that she has to be held accountable somehow via the legal system and being held accountable by karma isn't enough.
What you don't seem to realize is that suing is a major PITA. Even in a straightforward case, there are lawyer costs and time costs and it impacts your entire life. Often times, when you are in the midst of a law suit, you feel like everything is on hold until it gets settled. And it can take forever to get to the courts. There's always the change you'll lose (even if the case seems air tight) and have big bills to pay off. And in a case like this, you are opening up your personal life to inspection and misinterpretation. So it's really risky on many levels.
It's not worth the cost to most people to sue unless they have some real damages or some sort of major wrong that needs to be righted (like a corporation is hurting people). I just don't see what Kelly could gain from suing this woman and I'd be very surprised if he goes that route.
In the meantime, this woman is a laughing stock. Her boyfriend will probably quietly dump her and she's notorious enough that she may have trouble getting jobs in the future. She'll definitely have trouble getting dates! So karma is going to smack her down better than any lawsuit would IMO.