Is there anyway to see if a Key still works?

You know, you could do a whitelist giveaway like other people do sometimes. "I have some keys I want to give away, but not sure if they still work. If you join my whitelist you must agree to delete giveaway in the event that they don't work." That's the best way to avoid assholes that refuse to delete giveaways. ;)

You should have a good idea of which ones you definitely activated. Can always cross check with your account and check the date of activation on existing games. :)