I've had like, once, when an assassination triggered at under 100% plot power, but that's been over 300+ hours. So at least cross 100% plot power.
Also, can you declare war outside the realm? Go after some pagans if you can. If you can't, try to work on assassinating the Emperor or forming/joining a faction to lower crown authority. The assassinating emperor is to try and get a regent in place who might lower crown authority, they tend to do that.
That's what I was hoping to do but whenever someone tries to do it, king's foreign allies roll into town. So at least I will have to see my king dead first. Also half of the world seem to have fabricated claims on me, so whenever I revolt, some Austrian jerk rolls into town.
Not sure about outside the realm, but everyone who's on par with me in terms of levies had been eaten by other nations.
What does it mean if I have "holding of wrong type"? I tried to get rid of this and accidentally granted a country to my nephew.