Looks like Tom's got you covered mostly, but I'll chime in as well.
1) Yes, it's correct that the fields you can't touch are only editable by moderators, and are used for filing your concert in the proper area. You actually choose them when you first import the show, by choosing the "etree" area and then choosing the band.
2) Keywords are great when used properly. Keep in mind that all of the other fields are searchable as well, so putting the venue/city/state there is generally pointless, but the nearest big city is useful, as well as a musical "style" if you want to put that in there.
3) The "?" skipping thing is definitely an annoyance - it also comes into play when you have a venue or some other line that starts with a number (9:30 Club, for example). The parser is usually pretty good but some characters do confuse it now and again. I'd suggest using "Unknown" instead of "?" so that the parser knows it's reading a track name and not some weird variable. The only way to fix that is to check the show back out and upload a new text file *before* you import. Otherwise, the Flash player and mp3's get created and tagged with the wrong info and you have to delete all of the non-FLAC files and re-derive.