Originally Posted by DLGrkItalNY

You're most likely out of luck. Especially given you're going from one lie-flat to another so it's not a seat-type downgrade in a sense. You pay for transportation from point A to B, not for a specific seat unfortunately.

That said, someone who travels as much as you and seems to have history with Delta, should know enough not to rely on Delta to get a plane on a certain route at a certain time...