That doll thing can't be the god of jealousy. There's no point to bring Youta in his world to lift his curse which I suppose can do it by himself.
In his first "jump" Youta saw for a moment a naked (middle-age) woman so if the doll is that woman then maybe she is Noah's mother. If it is not a woman, based on the metallic hand, the doll can be Youta from the future??? But Youta lost his left arm, the doll has a right metallic hand so maybe Youta lost the other hand in another "jump" or they are not related at all.