1) -30dBm > -60dBm
2) FER(frame error rate) means the ratio of recevied good packets to overall transimit packets

Sensitivity means beyond the limit in spec., the FER > 10% for G mode, FER >8 % for B mode

3) "-20dBm" or "-12dBm" is strong signal level. If there are two walls between AP and user. I think the signal stregth is very weak. So I think this value is unreliable.