Apparently I’m still “barking up the wrong tree.” It looks like PFC is similar to XON/XOFF control, which is not at all what I’m looking for. What I want, and what is displayed but not explained, is how to direct traffic of priority 4 or higher to one of the lossless queues (or TCs, whatever they are) and anything lower to one of the lossy ones. There is no configuration option described for doing this, which is what my understand of CoS was.
I’m generating my VLAN tags within software using libpcap, and they’re being extracted by the switch prior to sending them out, but they’re apparently being ignored, due to lack of a suitable configuration, which apparently is not the default configuration.