I just wish I could fix it....
I'm sure the pred has a lot to do with the panting, and at that high of dosing, it can cause weakness, too, which I'm sure is adding to any weakness from the loss of red blood cells. It sounds like he's still doing okay, considering...he's eating and drinking and that's good.
Please let us know how he does with the Imuran, I'm hoping for the best.