I had a terrible time getting my galgo, Cruz, to eat when he was diagnosed with CRF. He completely refused any of the prescription renal diets or homemade renal diets. I kept him eating for a while with canned tripe added to his regular kibble. I used the Solid Gold canned tripe. Pepcid helped with the nausea for a while too.
I'm so sorry you are going through this with your sweet Jake.