In the past I've always calibrated all speakers using pink noise and set all db's the same.
I've never understood that part of the Avia disk either. I try and calibrate it to my mains then eventually give in to the temptation to adjust it myself anyways.
Same here.
I usually calibrate the subwoofer to my left main and just skip the subwoofer calibration for the other speakers. My thinking was the additional test sweeps for the other channels was if you were say running stereo, tri, quad etc… subwoofers you could calibrate each speaker + subwoofer pair individually. Never read that anywhere but it was the only thing I could figure it would be useful for.