You know what?
If I knew gods exist in this world, have a conscience and are responsible for all the natural disasters that happen… if I knew that a god can make a volcano erupt, or set a forest on fire, or ravage a village with illness…
I'd go straight for Amaterasu's head. I think that's what Father's going for. And frankly, it will make this manga much more interesting if he does and succeeds. He can have his final confrontation with Yato later, but if it happens before his final plan gets set into motion, it will be just another garden variety last boss battle.
Father is one of the great villains of contemporary manga. I want him to have a taste of victory even if he's defeated in the end.