I don't like Arnie for Kallor. I remember the description you mention of him, but I got the impression that he was fairly skinny looking; old, skinny, but still fit. The oddly strong wasn't him looking strong, it was an ephemeral quality.
That's the impression I got anyway... *goes to have a look*
Looking at the wiki, he is often described as gaunt:
"He was gaunt, but then, he had always been gaunt. His thin, grey hair was unkempt, drifting out long in his wake. His beard was matted, knotted with filth. His eyes, icy blue, were as feral as any beast of the plain."
"But this man was neither dying nor weak. He walked with the stiff purpose characteristic of the mad, the deranged.'
I could see Walken managing that, I couldn't see Arnie doing it.
Keith David seems way too buff to be Kellanved. I always thought of him as fairly wiry. Actually, I think of him as a slitely less ridiculous looking Pust.
"...a small black man with gnarled limbs and short grey hair. Or so the pretence. At first glance he looked like nothing more than a withered-up old gnome."
Idris looks like a good Kalam and Neeson for Wiskeyjack too

Oh and the Stormy suggestion.
Cheadle for QB I could see, but I've always liked Lance Reddick. His frame is great and his face is perfect. It's hollow enough and some of his looks are just so QB.
He's also 6'3" and QB was supposed to be tall (though height is easy to change for a film, still another plus)
And a smirk for when you look over after realising he's got you
I really like Jack Earle Haley for Fiddler

And Bob Hoskins could probably do Kruppe. I could never think of anyone for him.
Bane version of Tom Hardy is a good call for Brood.