IF he had a remicade recently he may need to switch biologics. If he is due shortly for one then he may need it more often and/or a higher dose.
In the meantime I would go to a totally liquid diet - if he's in enough pain then he may be willing to do it - boost or ensure.
to make it less icky, serve it very, very cold in a covered cup with a straw. Have him stick to one flavor and sip some every so often. Don't try to get him to do a lot all at once. He should stick to one flavor for at least 3 days before he gives upon it as he will get used to the taste if he's persistent.
Be sure he gets enough water, especially if he is having diarrhea.
Keep track of his symptoms: # BM's, D or C, blood in stool, pain 1 - 10, activity level - can he do normal activities or not, etc.
If he is suddenly in severe pain, unable to stand or straighten up then he should go to ER ASAP. If he collapses that is a 911 call of course. Same with vomiting red blood.
I am so sorry that he has gotten worse. Hopefully the GI can find something that will help quickly. Probably prednisone I'm sorry to say but maybe an immediate Remicade treatment will do the trick.