The boards came back and there are two errors (so far).

1. The optical receiver I sourced is only good to 500 kb/sec. The optical audio stream I’m trying to decode is way faster than that. I’ve ordered some of the 10 MHz variant. The datasheet for those says that they recommend a series inductor on the supply pin, so that’ll be a change to the board I need to make. 
2. I made a mistake wiring the mode pins up to the decoder. I’ve asked for mode 4, but I need mode 2. So that too will need to be a board revision.

I was able to test this by poaching the optical output stream from my Amazon TOSLINK decoder box. It sorta worked, but the L/!R signal was way wrong, so I will need to lift and rewire M1 and M2 and try again. If I see correct audio on the scope, then I will feel good about my chances.

EDIT: Upgrading the optical receiver to the TORX1355 fixed the first issue, and lifting the two pins and using bodge wires fixed the second.