The dog really is not on a balanced diet. Organ meat (aka liver, heart etc.) should only be a very small PORTION of the meat fed, not the main source. Over-feeding liver can cause diarrhea (which you already seem to have had a problem with). Liver & organ meats can be somewhat inflammatory, esp since the LIVER is a FILTER for all the toxins etc. in the original host's body. In addition, in a real prey model diet, it would only be a tiny part of the entire carcass.
If you feel that duck is the only safe protein, stay on that, for the time being. BUT... according to a recent "Whole Dog Journal" article on the benefits of feeding a raw diet, in 95% of the cases of protein allergies, dogs were NOT allergic to the same meat, if it was fed raw, vs cooked. Cooking chemically changes meat, as well as reducing the nutrition available from it.
Most dogs need to eat a variety of veggies (too) for fiber, & various vitamins/minerals not JUST meat & bones. Many green leafy veggies are very high in cancer fighting antioxidants & raw diets suggest you switch around both the protein source AND veggie slop mix (often) to make sure you get a wide variety of nutrients, and avoid the dog becoming allergic, by not varying the diet. Wild or feral canines/lupines eat a WIDE array of foods, per month. You also have absolutely NO fish or fish oil, to provide the important fatty acids (Omega 3 & 6). Almost all commercial dog foods now provide some version of fish or fish oil because it has been found to be very important to their well-being (both for coat & to help soothe inflammation/allergies).