It worked! My three beeps are back for the first time in over a month. The name matching process actually works. What a relief. Pre-check has really spoiled me.

Here's a recap for new visitors to this thread:

All three of your names (first, middle, last) much match in all the following records:

1) Delta Skymiles record
2) Secure Flight Information record
3) Boarding pass
4) Individual reservations (if you bought tickets before fixing your name records, each reservation will have to be individually reissued, which can be done by a phone rep).

Caps or non-caps do not matter. My Skymiles middle name is not caps (except for the first letter) and my secure flight information is all caps.