The Packmaster is still a little bit weird for me.

He is by definition a division commander and can lead every friendly squad in LD distance. In the rolebook the term is direct but this means the same, or?
But then they stated out he can command every Wolfpack unit including the Wolfbanes and the Wolfbairns.
Does that mean he is a restricted division commander? Pretty much a division commander light?

And he can command every kind Wolfpack troops but I can only buy him if the grunt unit is a Wolfbane or Wolfbairn Commando?

I would expect you can buy a Packmaster for each kind of Wolfpack troop (incl. Grunt Commandos) if he can command them, too.