Use ADVNULLANTENNA as your identifier.  The 372 firmware isn't new enough to recognize newer calibrated antennas.  You should be able to connect to your base even if the coordinates are incorrect so repeatedly doing the PPP/OPUS thing isn't really important until you know you can connect.

I don't use the built-in NTRIP client on the 372 so I'm not much help.  I use an external ntrip modem client and feed in through the unused port on the radio. On an FMX you have to change the reference/station ID to 250 for it to accept external serial data.