Q:

Betraying the legion while organising peace talks

I distrust the Imperials (Legion) and want to join the Stormcloaks – always have. However, I (accidentally) completed the first quest of Joining the Legion (“Clear out Fort Hraggstad”).
I then started the Season Unending quest line. I was able to talk Ulfric into joining the peace talks, but not General Tullius: as you may know, the only dialog option I have there now is to swear allegiance, which triggers the Jagged Crown (Imperials) quest.
However, according to the wiki (and other answers on the web), I should now be able to betray the Legion and give the crown the Ulfric but I am not given this dialog option. In fact, I am now in possession of the Jagged Crown and yet I cannot talk to Ulfric at all, I just get a stock phrase about coming to the council from him.
How do I enact the betrayal? How do I join the Stormcloaks?

I know that there are several, shall we say, complications with these missions. However, my particular situations doesn’t seem to be covered. I guess what I am looking for is confirmation for whether I really cannot join the Stormcloaks any more. I’d probably start all over then, which would be a shame (I really don’t want to join the Imperials, even though I’m a High Elf).
(I’m unfortunately on an Xbox 360 so I cannot install unofficial patches or use the console.)

A:

As long as you haven't given up the Jagged Crown, you should be able to switch to the stormcloaks.
What I expect has happened is due to Season Unendiung -- specifically, you'll have to try to finish resolving the peace talks (in any manner of your choosing), before talking to Ulfric again.
If that doesn't work, you may be out of luck, because the required quest setStage shenanigans require the PC console.

