I think this puzzle has more Saturday-style trickery than my average themeless. You've been warned.
My first (and most likely only, for a long time) shot at a themeless with an open middle and minimal amount of 3s (just 4). This required some fill compromises (I really, really DO NOT like the "Odd Job" answer at 39A - explanation in comments). 34D isn't exactly sparkling fill, either. Besides the middle, the 5x5 NE/SW corners also turned out to be hard to fill cleanly.