Thank you all for your input and feedback. This has been an extremely frustrating experience with Delta not just on the Athens flight back from Europe but also on the front side when we are flying from JFK to Barcelona on the 13th. That one went from an 8:50 pm departure, to a 10 pm departure on a totally different plane so we lost our premium select seats, to they changed the plane again and rebooked us to fly out the next day (14th) so we had to call and get our seats back for the 13th flight... so needless to say, it has been very frustrating.
I honestly think after reading all of your feedback we are going to shift to a later flight. Even if there is a slim chance of making the 10:20 am flight, if we miss that then we could potentially be stuck in a whole other world of problems. It is better to just take the 2:50 pm flight that will connect in Paris and then to JFK. It will mean spending the night in JFK and flying back to Austin the next day, but will be the safest route vs trying to roll the dice.