OP was 3 lbs overweight, for a GOLD member they should have given him some leeway--but per the "rules" they didn't have to. A related thing crossed my mind, who certifies the accuracy of AA (or any airlines) scales?
Would it be the local/state agency in charge of measurements, like the ones that certify gas stations? I feel like I've seen certification stickers on/near some bag scales at airports.