Some basic questions about Nexus QoS

Sorry if these questions are stupid... but I did put forth some effort on my part. I read the Cisco Nexus 9000 Series NX-OS Quality of Service Configuration Guide, Release 7.x (read all chapter). But a few things are still very murky.

For starters, nearly all the configuration examples in that guide use 'match cos' in the class-maps.

The network I'm working on uses a DSCP-based QoS configuration everywhere.

I've tried the config examples in the guide and with match cos in the class-maps, nothing hits and everything is best effort. When I write a class-map strictly matching dscp value, then I start getting hits and stuff is queuing properly.

My question is: isn't there some way that I can automatically map DSCP values to a COS value, so I can write the more simple short-form QoS configs as featured prominently in the guide?

Is this what the table-map is for? And if so, is there any really hand-holdy ELI5: type guide to using them properly?

My next question is, can anyone explain to me priority-flow-control and what it actually does, because it looks like black magic to me. When I read about PFC, it seems like the two servers are the ones sending the pause and resume frames, so why does the switch even care? What does the switch actually do when I configure this?

Thanks for any help, sorry about the noob questions.

EDIT: Guess I have a 3rd question also. I understand that I have to do TCAM Carving to do what I'm wanting to do. But how do I know which TCAM region to steal from?? You have to steal in big increments, it seems very tricky.