A bit surprised at the hostility toward OP by so many here. He may have unrealistic expectations about compensation, but he wasn't asking for the moon, and was willing to pay (apparently quite a lot) for what he wanted.

FT is all about getting the most out of your experience, often without paying for it, so why slam OP for being disappointed? If DL had to shift seat assignments, seems that breaking up a pair traveling together on full fare F should have come last on the solution list. Perhaps the lesson here is NEVER pay full price because it doesn't confer the privilege you (rightly) would assume.