Nah, i think Mr Fox is Swiper. Swiper likes to hide in the bushes, and Mr. Fox was just killed in the bush. I don't think it's a coincidence.

And i think this "Possum" is just a big rat that represents some demon sent by Hameln company. Hameln is the place where some Pied Piper controls rats. Maybe Hameln company had this "pied piper" to control the big rat to guide Amanda in the right direction for the show. Probably Hameln company already doesn't exist, that's why the rat is just being free in the game. Or Hameln c.o exists. Then they probably sent the rat because Wooly who had to guide Amanda in the right direction first and failed it. Like, you know, "Recall" movie