I should probably post a compiled results file again sometime. It's a little overwhelming at first, but if you're insane like I am, it's fun to fiddle with on occasion. I can look at silly things like Called/Swinging Strike out rates, and a gazillion other things that might or might not make a difference at all.
The defense stuff, though, I'm pretty confident of. If I could ever get it to individual players, I'd trust it a lot more than OOTP's ZR.
I've done work that can get down into individual players, but to do it you need more information than the game gives you in its game logs (the data is easier to get at in the base .csv files, but only Matt can manage those for us). That said, if I think about it, I might be able to use the box score html files to back-calculate it. That's a lot more coding work than I want to do right now, though.