About vanaduke's story, everyone know that almire was destroyed by two kingdoms that agreed on doing that since they considered almire as a threat. And then vanaduke alone destroyed both kingdoms. But nobody said a thing about those kingdoms, but i have a theory: Almire was destroyed by king tinkinzar and other king, the gremilins survived vanaduke's fury thanks to the clockworks, and they stayed there, haven seems to be only one of the cities that gremilins made (i'm assuming that since the clockworks was made by king tinkinzar and because of the various gun puppy statues around haven), the other mysterious kingdom is hidden somewhere, and ruins about those three kingdoms are hidden around the cradle, and those ruins would make rather interesting new areas.
No, Almire was from a different planet. Tinkinzar thanks to outside help(read all echo stones/Speak to the Gremlin Stranger to understand), Got chunks from Almire's castle and other planets and put them into the hollow insides of Cradle.
The other two kingdoms I think is the other castle places(Scarlet Fortress and Jelly Palace) That was taken over by Vanaduke when he gained his powers(Hence the Almire Symbols). Haven was made by the Strangers(either inhabitents of Cradle already along with the Gremlins or got taken there from their planet and took residence on the surface) and the Birdsong Trading Company and Haven Treasury wasn't made by the Gremlin mechanics. The miners either made/found these statues based on a gun puppy god(Miomni could be a god). The god was the design for the Gun Puppy constructs.
Also Vanaduke didn't defeat them alone, he had an army of fiends helping him.