Hello all! I received a lot of support from this forum trying to get this project off the ground, so I figured I should share some of the results as well.
Warning: this project is stupid. Maybe the dumbest thing I've ever spent my time on. But...
Well, bad news. Back to 9 blinks and the capacitor is still definitely installed. Seems like I may have torched some other traces with my bull-in-a-china-shop mentality.
Definitely connect Pin 5's trace, but per the schematic I don't think that...
Good find and fix.
I'm getting 9Blinks with sketch issue and 15 Sec Restore recovers that. So suggests real hardware issue won't clear 9Blinks - but it can for software issue. For software Button uploads still worked as well.
Upon further inspection after removing the teensy from the protoboard, it seems like I've blown up C28. Not certain what that would have to do with my problem but I'll try dropping another 2.2uF cap in its place: