Whatever Wilbur's story, he's family, and so are you Adrianne. I think you're on to something with the runner. Might be worth taking a few minutes to analyzing everything about his surroundings, putting yourself in his position. If you had a rod in your leg, what would cause you problems? As far as not wanting to leave the yard, he's probably feeling vulnerable right now - too vulnerable to expose himself to the outside world, although should you get a few pounds on him, he might feel well enough to just go out on the street and stand for a few minutes. Venturing out even for a few minutes will make him feel so much better, as long as it's on his terms.
We will keep praying for a good appetite, rejuvenating rest and maybe a visit from a new friend to brighten Wilbur's day.