That part that I bolded, that is a very classic sign of advanced kidney disease. That happens when the toxins build up so much because it's not going out when they pee, that it starts making their bodies and breath smell almost like urine. I believe it's actually called uremia, can't remember for sure.On dec 30th I went out of town my son was sitting with him and my othr two cats my son called me on the 2nd and said THAT mvlovin was hardly eating and was just sleepin my son didnt have enough money for a vet visit so he found a coupon online for a free visit and took him to the vet when he got there they looked at him and said he was dehydrated and gave him fluids my son also told the vet that their is was something wrong with his mouth she looked at him and said she didnt see anything. I got home later that night when I got home mclovin can and he sat next to me and he smelled like he had been rolling in the litter box and by the next morning his mouth smelled awful so monday which was the next day I took him to the vet and had xrays and blood work done the xray didnt show anything and the blood work took a day to come back and the vet was close the next day but they did give me meds for the ulcers and I had to feed him baby food and give him water so by wed he was worse so I took.him back and this time they keep him they said he was in kidney failure I called the next day and he had passed I couldnt belive it I wish I knew ahead of time maybe I could have done more for him im so heartbroken
For what it's worth, by the time you took him to the vet, it was probably very far advanced, and there wouldn't have been much that could have been done other than to make him comfortable.. They could have hospitalized him, but not sure that was something you could afford (I know I couldn't). And please don't feel bad. Cats are VERY good at hiding their pain and discomfort.