my question is why he did it?

Yeah i recon he did, picked up that issue last night mainly for the battle element though enjoyed the story a lot more than i initaly thought i would. I wouldnt mind asking Daken the same question right now.

I think it was part of some trick that Daken and him has planned later again their fathers
Because he doesn't want to die, he wants to kill the Hulk

Daken stopped when banner threatened Wolverine only because he was to be the only person who kills him, not because he cares. The same thing happened when Deadpool was about to kill Wolverine. Daken saved him, not because he care, he did it for the chance/right to kill his father. 
 
As for Skaar I agree that his child side hates his other side, look at Bruce and Hulk, same body but completely different personalities. Banner has tried committing suicide a few times if my memory serves me right, so it could just run in his jacked up family tree lol

" Yes, in human form (or as human as he can be) Skaar feels ashamed for what he did on Sakaar. He hates his monster side of himself, so instead of living with it and trying to control it he just wants to die and be put out of his misery. Skaar (hulk) form seems to have a whole nother opinion on it, he is ok with his savagery and seems to believe he is the strongest and unstoppable  Dkane was happy to help out and then Banner realized that Daken had the metal from the muramasu blade covering one of his claws and ordered Daken to stop unless Daken wanted Banner to kill his father (im suprised Daken cared) "