[jagasail]

Have you used the MiniPlex configuration app to verify that indeed the missing NMEA data 1.) exists and 2.) is being received by the MiniPlex42BT?

Even more basic - do you have the right set of instruments to generate these sentences? The one required that stands out is the Raymarine fluxgate compass. You need that to get the magnetic heading, required for the three sentences you're not getting. You probably won't get these from the GPS. Some Garmins, notably the etrex, have a fluxgate built in but the few manuals I looked at indicated they were generating a different sentence.