Ideally Ammosh should be eating a diet that is designed to help with the management of renal disease. Renal diets are generally low in protein which is helpful in management of progression of kidney disease. Kidney disease, however, can also make pet's nauseous, which could be contributing to Ammosh's symptoms.
If Ammosh does not like this renal food (they are known to not be very palatable diets) you could try offering him other diets or forms of food as the ultimate goal is for him to continue eating. Liver has not been shown to be beneficial in renal disease, but you could try other things such as boiled chicken or hamburger.