i was diagnosed with crohn's in 1999/200. flare ups can be caused by stress and if running helps alleviate this then running definitely helps. during times where you aren't necessarily having a flare up as such, but things have been grumbling you might find it harder to run. as far as diet goes, it's pretty much individual - what one person can tolerate another one can't. i find eating a well balanced diet, not drinking too much alcohol, not eating spiced foods and high glucose foods, not overeating, and drinking plenty of water have kept things at bay. also some people find a high fibre diet is good whilst others find it makes things worse. running unsettles the gut anyway, and exercise is always the doctors advice for people with constipation, so running when your gut isn't great in the first place can exaccerbate things. if you take your meds prophylatically rather than just upon flare up it should help to reduce the inflammation and keep things at bay.
at 119lb i was burning approximately 80-90calories per mile. i'd not bother with looking at the calories, as said, the machines are pretty innacurate. if you feel you're burning too much then you need to eat more, see the extra food as a medicine, even if you're not hungry but you need the extra calories, just eat. if you're not meeting 2000cals/day and running 46miles/week plus the cycling you should be losing weight. i'd suggest knocking the cycling on the head.
i did it last year, really good race. it's done as a time trial so no mass start. we parked at the car park just a few minutes away from registration last year. you can get the train back (station next to car park too). not sure about options for parking in birmingham. i came down from glasgow for it.