Will Falconer, DVM Moderator
The first thing to realize is that this dog has chronic disease. IBD is but one form of it.
Second: neither diet nor anything conventional medicine offers can cure chronic disease.
And finally, chronic disease can be cured with professionally prescribed homeopathy (it's far, far from DIY or from combo remedies or from someone calling themselves "homeopathic" who's not studied it in depth and who doesn't practice it mostly or solely).
Here's a video I created to help you find a worthy homeopathic vet. Note: Distance work is totally possible.
With a true cure, this dog can eat anything a normal dog does. It'll take time and attention to symptom details, but cure is possible.