@Umesan 1. He saved the whole bloody country by sacrificing himself in the war against the demonic beasts. The father did sacrifice his own life for real. That's like saving a million families or something? I guess still not enough for an Asian author, haha?
3. They could just not care. The crown prince already promised not to mess with the MC's family. That was the deal. Just ignore them. If they still push forward, make a divine statement through the clergy that the royal family has sinned and lost the blessing of the divines. Let them deal with that in a country so religious. It would be beneath deities to go and slay mortals personally, anyway. This is the primary problem of this work in general: Origin and Ellen don't act in a way befitting their station at all, in relation to mortals (it doesn't matter how they act back in the spirit realm). It's because they act like that that the king feels like he can plot against them. If a goddess acts like some petty mortal, you might as well treat her like a mortal.
In my opinion Origin shouldn't have shown herself to anyone in the mortal realm aside from perhaps the brother and the grandmother privately. Going to a bloody wedding? Jesus Christ. Yes, that's like Jesus coming down from the Heaven to attend some random dude and dudette's wedding suddenly, in flesh, for everybody to see. Ellen as well should have kept her mingling with the mortals to minimum, unless she could mask herself perfectly and not reveal any powers or spiritual presence. This is knowing your position and realising your effect to your surroundings. If they care about the mortal world, then don't affect it in unpredictable and whimsical ways. And especially don't get involved in bloody politics.