Part of this, however, indicates that the file that is output / loaded into AAM should include the UserID, a tab delimited, then your extra fields which are then comma delimited. Is it possible to output a file from AC that is tab delimited for the first field, and then comma delimited after? It looks like you also don't use field headers, but X="Y" format. Can AC also output this kind of format?
Not sure there is a default option that lets you use different characters to delimit several columns of a line in a file export (at least through the UI).
Can you specify which version of Campaign you are using so I can make sure if there are ways to do it? (I'd assume it is possible with custom code with Campaign Classic - which unfortunately is not my specialty - while it is probably not the case with Campaign Standard).
Also, have you considered using the integration between Campaign and AAM? I'd be interested to provide some feedback to the team in case it doesn't match your requirements.