sher brings up a good point; vassalage. You could perhaps hold out long enough to join a nearby king? Takes about a week I think, that might be too long. But there's a window, I believe, between the return of your emissary and your actual joining (have to swear to the king) to recapture Ethos, should you lose it. They won't stick around, and they won't leave many troops behind either. Should be easy to retake with elites, which should pretty soon be easy to replace, especially if you have a walled fief.
The method described by sher is the way I play this game. You see, I'm not really that good at this game, so I avoid risky plays and like to see the odds stacked in my favor.
My recommendation in general is to play as a vassal. Grow under their protection until you can grow no further, then gut the kingdom, bringing with you the friends you've made in your conquests and then consume your host nation, now weakened by the loss of their most powerful lords and holdings.
Another thing that's good to remember; this is a sandbox. Sometimes it's just not the right time. Learn from your experiences. Adapt. Evolve.