Not overkill since I feed mine double that.These older amps tend to need cap replacements so I would shop around and pay a bit more for a recently serviced one. Replacing caps will cost more than the amp normally.
Sounds like you hamhandedly force the screws in without aligning the holes perfectly. I suggest shoving some blutack into the threading. I recommend taping the pads directly to the housing so no more free rotation. I've seen people try to use the hifiman rings to mount Vegan pads and I look at the setup with pure disappointment.
Probably is half of max, but Krell also underrates all their output numbers too. I'll only have music on that setting for very quiet tracks. It's usually in the 8-9oclock region.
You also have to factor in gain for the amp. I got no idea what gain is on yours. Low gain will give you more volume play.
I use a 24 step passive autoformer volume control and I've got enough play. It never goes past 12oclock for me but I can find the right volume. More steps would be nice but it's fine. This is also comparing with the exponential curve of my Master-1 which still doesn't give you a ton of play unless your amp can use ACSS/CAST too which has a lower gain.