Sorry to hear about his pains, bloating is very uncomfortable. I'm newly diagnosed as well and when I'm flaring my stomach gets so big that I've had people ask me if I'm hiding a basket ball!
I'm tapering down on a steroid as well and trying out different medicines. Diet really depends on what kind of day I'm having, if I'm particularly bloated I've found that liquids (broths, jello, pudding, Boost/Ensure, smoothies, popsicles) really help get through it. I try to stay away from pineapples, berries, and coconut as even blended they can be hard to digest and they seem to make the bloating worse, but everyone is different.
I don't do juices just because they tend to make me gassy...:blush:
For normal days, I stick to a low fiber diet. Some people have a hard time with proteins, I found I can tolerate eggs, chicken, and some fish.
One thing that's really important is to make sure he get's all of his nutrients! The diet will usually come with trial and error but just make sure that no matter what he eats he is still getting the good stuff (even if it is in liquid form like Boost or Ensure) Good luck!