I started feeding raw 7 yrs ago because of a dog with IBD. At the time, there weren't any kibbles he could eat. He was still on Metronidazole when we started (he was about 2 1/2, too) It worked really well for him, he was able to get off the ABs and just takes them when he has a flare up. A little over a year ago, I tried to feed kibble in the morning and raw at night, to save time & money. I feed Taste of the Wild Pacific Stream. I do this every day with my girls, who do not have IBD, but even though the kibble doesn't have any of the foods that I know trigger an IBD episode, he still can only eat it about two days a week.
First, you have to figure out what foods your dog is sensitive to. Whether or not you can do part kibble and part raw (or home cooked) depends on if you can find a kibble she can tolerate. It seems that there is something in the processing of the food that affects a lot of IBD dogs, but not all.
If she is good with duck, adding the whole carcass sounds excellent! Good luck!