Re Morgoth drawing in the dirt with a stick -- well, you know, I'm not sure what there was to do in Angband all day, so who knows what else he got up to?

Given all the effort they're going to to make Thorin a ~sympathetic character~ with a story arc and all that, I wouldn't be surprised if they did give us more of Thorin's history, so we might very well see more of Thrain and that time period! And it would be cool if the movie did make the "this is one of the dwarf rings that the prologue to FotR mentioned" connection... I don't think we'll be seeing any of the others, though? That would be too much of a digression, even in the books it's only really the same bunch of dwarves we see, and no other kingdoms.