you were asking for the impossible from QR. The staff checking in at BKK are probably not QR staff anyway but contract agents who provide checkin service for multiple carriers

The fare rules are AA's - you purchased an AA fare not a QR one, so not something that they would have. You would need to go to AA for that, Also Fare rules do not have luggage allowamces listed in them as a rule

Their lack of interest might well be more that it was not a problem that they were ever going to be able to solve - this was between you and AA

Fortunately you found a better option than trying to claim luggage fees back from AA. I suspect that you would have ended up having to go to court for satisfaction