Update to my post directly above:
So a week later all that's happened is they now have the correct DL number on my former NW account. But my registration at the former DL account for the latest bonus (500 for every $50 cumulative) did not transfer to my former NW account, the earnings history for the two accounts is still separate, and I only have VIP status for next year in one account.
So after reregistering for the bonus, I now have an account at SkyMiles dining which I can actually use (the former NW one). But I still have to look at two accounts if I want to look at my dining history...