Well, we're all pretty much stuck in a "trial and error" pattern, until we can find a routine that works for us. I've always tried to take a pragmatic view of this disease, and when what we're doing is not working, and we've given it a fair try, then maybe it's time to consider trying something different.
Lesley, since you can't seem to find any food that doesn't cause some sort of reaction, I believe that if I were in your shoes, (and I was, about 9 or 10 years ago), I would try either 6 mg or 9 mg of Entocort, per day, probably plus one or two stool softeners. Here's why:
Your inflammation level is high, (as demonstrated by the undigested food in your stool, even though you're predominantly having C. The undigested food indicates that not only your colon, but also your small intestine is inflamed, (and that's why you're having the pain symptoms that you describe - if your small intestine were were not inflamed, you might still have D, but at least the food would be properly digested). IMO, poor digestion is going to tend to perpetuate the reaction, whether it's marked by D or C.
This is a long shot, because the Entocort will provide no benefit for the duodenum and the jejunum, but perhaps enough of it will be absorbed by the ileum and the colon, to provide some degree of inflammation suppression. IOW, I'm thinking that maybe by suppressing the inflammation in your ileum and colon, that may suppress your total inflammation level enough to allow your digestive system to shift gears, and begin to digest food again.

It may not work, but what you're doing now doesn't seem to be working, either.
Entocort can only make the C worse, though, so if you try this, IMO, you're going to need to up your dosage of stool softener significantly, because it's not doing the job, even without the Entocort.
These are uncharted waters, because C is more difficult to treat than D, to my way of thinking.
The reason why warmer foods or liquids cause more pain is probably because the higher temperature causes additional gas expansion, causing more pain from any existing bloating. That was always the source of my worst pain - gas that I couldn't get rid of for days at a time.
I'm not recommending that you should try this - I'm just throwing it out as something to think about.
Tex