There's definitely a marked improvement! We got to look at the October and December X-rays side by side, and there's a difference clear to the mostly-untrained eye. In October, you could still see where the breaks were quite easily. Today? The bone graft has definitely taken, and the bone looks almost totally solid.
Our dilemma: The screw farthest down in the bone may be interfering with her extension. It's *very* close to the elbow. If it's in the joint itself, she has a risk of developing osteoarthritis. There's apparently no way to tell if it is other than going in and taking it out or doing a very expensive set of tests. And even if the screw is removed, that may not fix her limp. And surgery is $600-$1100, depending if she needs general anesthesia.
I would feel like a crappy cat-mom for wibbling on taking the screw out, except.
She's in good spirits (well, not right now because she's pissed at us for taking her to the vet). She runs, she jumps, she goofs off with the other cats, she chases her tail; she does have a marked limp, but it truly does not seem to be bothering her at all. She's in no pain or distress. And the vet was very clear on the fact that she can't be certain if the screw if a problem at all.
My gut reaction is that she's probably fine. The vet seems to be treating this as a precaution - the screw probably isn't in the joint. The plan is to watch her over the next few months, be more rigorous about the PT, and hope that her extension and mobility improve on their own.