I was able to learn more about this stuff this week by poking around EF and just asking folks who are familiar with this stuff. It seems like a fare basis can be whatever bucket (eg N) and can book into another (eg P, as in my example).
I was able to search for the fare in EF by searching for the P fare, and found the farebasis that began with N. Turned out to be easier to find the fare than I though before, must've done something wrong earlier.

As for crediting, it should credit into the fare bucket that it's booked in, not the fare basis bucket is what I was told by a phone rep, and also example in EQD earnings on AA from a past itinerary.

Henry