I spent a few hours researching scat and tacks on the net last night. I couldn't find anything with scat like that except rabbit, but it seams a little small for rabbit to me. It's only pea size.
The tracks, I think, are bob cat, but that was probably just one checking out the den for critters, and it was old.
I'm leaning toward the idea that rabbits moved into an old coyote den, but I wouldn't think they would do that. I would think there would be enough odor to ward rabbits off.