Then I figured that, after the Windows update I'd just performed, running any game as an administrator (typical for Koei games, for some reason) prevented the Steam overlay from running.
By then, I'd already removed my previous controller config, so I had to download one. Then I encountered an issue where every time I tried to perform specific button combos, I'd evade instead. Ugh.
I think I've finally gotten everything the way I need it to be again, but I've spent the two hours of free time I had this morning getting that taken care of, and now I need to focus on getting Ken up.