So, I finished Blood on the Ice quest, but I can't buy the house. I go to the steward Jorelif, and there's simply no such dialoge option as buying a house. I know of that stuff that usually says "help 3 people, I'll make you Thane and you'll be able to buy a house", but Ulfric hasn't got such an option. I've also noticed in the quest log, that even the quest is done, the part that says "Get help from Jorelif" is marked as not done.

Any help on this?

P.S. Any time I enter Ulfric's palace, there's that dialoge between him and his general about Whiterun's neutriality.

You can't buy it unless you do the civil war.. You can't buy it unless you side with Ulferic .. or after the war from the Imperials..

big bummer for me.

And is it possible if I end the war by peace during the meeting in High Hrothgar during the main questline?

The war doesn't end. All that really happens is some territory swapping. You'll have to either win it all for the Leigon, or go as far as Rescue from Fort Neugrad with the 'cloaks.

Okay, thanks!