Are you on sick leave? If you are, you may be able to work something out with the university (been there, done that -- at a different one, though). Or ask your GP to refer you to a nutritionist familiar with Crohn's and other diseases that can cause malabsorption.
My guess, from what you've described, is that the weight gain is from the prednisone. Remicade may have healed your guts beyond what the prednisone could achieve, but the water retention and your body's tendency to hoard fat are probably caused by the prednisone -- especially if you have a hump at the bottom/back of your neck, a puffy face, weight gain disproportionately in your upper body, etc. A lot of prednisone weight gain is actually water (there is fat, but it's not all fat. . .), so going on a strict diet may not be the best way to stay healthy.
Prednisone withdrawal sucks and should be done slowly and under medical supervision -- there are lots of descriptions of what it does to different people in different threads in this forum -- but when you get off it, or even on a lower dose, you will likely lose most of that extra weight.
In the meantime, make sure you are eating a balanced diet, staying hydrated, getting enough soluble fibre, etc.