Great read! You make several interesting points.
As for the drysuit, I confess I am at the (woosy) point where water colder than 71 degrees means I dive dry. We did the Naeco once in December and it was a comfortable 73 degrees. But, the U-85 even in mid- summer, and the Yancy and other NC wrecks in winter, are just a bit too cold to dive wet (while trying to do all those deco skills). My DS was probably my most expensive gear purchase to date, but it was without a doubt one of my wisest gear investments. (My one personal observation would be that, since it is so expensive to begin with, dont cut corners to save a few bucks. But, that may just be me.) I doubt I will ever dive wet with more than 3mm again. The manifold / valve shutdowns are a bit challenging in a DS, although I cant imagine what they would be like in 7mm. BTW, what were you using for backup tables, in addition to your wrist slate? I prefer Wet Notes / Dive Writes, which can be stowed in my DS pocket but am interested to learn what others have found that works.
In finishing our deco / tec course, after doing the first 7 dives in (cold) NC quarries, we (two of us) lobbied our instructor for making either NC coastal dives (like you were pursuing) to finish, or a road trip to Pensacola so we could finish the course on the Oriskany, as neither of us students were wild about going to cold, dark, spooky Joccassee in January just to get the 165 depth. He demurred, saying he preferred not to go with boat dives for the tec course dives, citing the unpredictability of sea conditions (as you apparently experienced), the time efficiency issues of getting to the site, getting geared up and into the water, and then back aboard, as well as the distance from emergency support, in the very unlikely but still possible case an emergency developed. We ended up driving 10 hours down to Ocala, FL, spending three days in warm sunny weather, and diving 40 Fathom Grotto for the last 5 dives. It was an OUTSTANDING training venue, by the way, and something to think about if sea conditions do not cooperate in the coming month.
Thanks for sharing your experience. It helps us all continue to learn.