Yep, but they record the full name + ICAO. I can check again, I have the testing/debug script which I used to parse the actual values returned from FSPax (I didn't use any of their code). But from what was actually returned that's what I used. I can modify that regular expression, but I'd have to test it and see. Do you have the latest version? Perhaps it's a version difference. But if it's working, then great.
Actually, I just looked, if you turn ACARS_DEBUG to true in your local.config.php, and empty the module/acars/log.txt, then export flights, you will see what FSPax is sending. If you can post that log file, along with the version of FSPax you're running, that would be great, I can take a look and compare it to my FSPax.
And yes, the flight ID has to match an existing schedule in your phpVMS schedules.
You can use both FSPax and FSACARS. FSPax for the passengers, and FSACARS for the PIREP and status. FSPax doesn't send status reports to the site, so you can only export PIREPS. With FSACARS you can have your flights show up on your live map. But it's possible to use both of them simultaneously.
I'll take a look at the FSPax export again this weekend if I get the chance to.