Yeah, the Genoskwa surviving really doesn't make sense. The Earth Magic thing doesn't make sense either because he was killed in a cave, yes -- but specifically in the Ice Cave. I know that Forest People are a lot tougher than humans, but he was literally pasted.
Why wouldn't he have come for Harry by now? It's not like everyone in the weird-side does not know where Harry lives. Harry might be the easiest wizard in the world to find. One need only find the nearest Burger King near the Svart-elf compound.