In game says that the white beast was seen during the day and what was told in the game is that werewolves are night creatures, so they would be mostly sleeping during the day. Could be another white werewolf, a stronger one. But could be another werebeast.
Sometimes I can be like that too, I can understand you in some degree. If it's Ruben, I really want to know his motives, why would he do that? Could be so many things.
I think he was THAT vague is because he doesn't know that much about the Father, he didn't tell everything he knows of course but I don't think he could have all the answers. I think the characters we know less about are people from Northcrest, putting werewolves aside.
I don't think he's a fake king, you described in the most perfect way possible: it's just a empty title. But I don't have any theories about why he is different from other ratkins, probably because he's older or something.
I think Scrap is different because he was born different. If I am correct he was born with albinism, making his fur being white, that's probably why he's short and pretty much being bullied. And because the ratking wouldn't help him it wouldn't be a surprise he doesn't like the ratking.