I have two theories.
Rya was raped by a brutal man and can not have children. At first I thought that a miracle would happen and they would have a baby. After reading about how both of them seem to be having the same dream, I'm wondering if she was raped by a goblin. and has part goblin in her. That is why it was made that she will not be able to give birth to another goblin and why Slim is chasing someone that he loves in his dreams.
Re: Ferris wheel.
It seems that the ferris wheel was more of a physical display of her suicide intentions when she insisted they go up on it and stay during part of the rain and lightning, but maybe that was a clue to what will later happen. Now, I'm thinking that maybe when the goblins come to the carnival that they, with their free passes, will go on the ferris wheel prior to any planned disasters and the wheel will get struck by lightning and many goblins will die instead if their intended victims.
I could be wrong on both accounts but, it's just a thought.
I hope that he doesn't have any goblin in him. In the movie Blade, the character fought vampires but, he was half human and half vampire.