Hang in there.
I will list some of some of my previous suggestions that might help you temporary:
1) Jini Patel Thompson has a nice liquid nutrition
powder formulated for these kind of situations. In short, it uses whey protein which you can easily get anyhow. L-glutamine on an empty stomach is also a component that soothes diarrhea.
2) For coating the soothing the gastrointestinal tract - slippery elm, marshmellow root, and deglycyrrhizinated licorice might do the trick. I know people suggest slippery elm quite here.
3) Low residue foods like rice, potatoes, cooked and peeled veggies might help. Bone broth is always good for the GI tract.
4) Vitamin D, fish oil and curcumin might also help, as those have clinical backing.
5) This may sound difficult with the prednisone, but try to rest and relax as much as you can. I am sure certain chores can wait until you get better.
Best.