Spent a couple of hours on the phone with Delta. The various agents I talked with were willing to waive the $200 reissue fee, but not the fare differential for my ticket. One agent tried to rebook my wife's companion fare but was unsuccessful and ultimately I was told variably that it either can't be reissued or only reissued in L,U,T classes (none of which are available on any flight the day we need to leave).

Currently I think the best options are either
(1) Wife and I fly separately, use 60K miles for her flight
(2) Change my ticket (~$400) and use miles for wife's ticket (60K).

None of the agents I've spoken with think the chance of U class opening up is good, although you never know. I plan to call again this afternoon and see if I can get a supervisor. I'm not optimistic, however, as I was told by multiple agents that "nobody at DL" has the authority to rebook the companion certificates in non-LUT fares. I guess I could try Amex, which apparently has the authority, but I'm not even sure who I would talk with there. Technically I think she's testifying as a private citizen.