The key is to keep him hydrated more than anything. When any living thing is going into renal failure, their body just can't process food and nutrients like it used to, making food, especially solids of any kind (even canned foods) very difficult to eat. They can go a long time on very little food, but they NEED water and lots of it.
If he can't drink on his own, get an eye dropper or syringe (the kind used for administering children's meds is a perfect size) and slowly drop water into his mouth throughout the day. He may do better with small amounts of canned cat food on the end of a wooden coffee stirring stick that he can lick off if he can't eat from a bowl like he used to. A can of food administered throughout the day in this way will go a long way. Don't bother with dry food anymore. I'm sure the vet told you this is too hard on the system when the body is shutting down and just difficult for them to physically eat as well.
You will probably have to create some sort of schedule, and administer water and food in small amounts throughout the day and night (at least that is what happend with a pet of mine) to ensure they are hydrated well. You'll find at some point, they just can't drink significant amounts or eat significant amounts in one sitting, so you'll have to go about it in a very slow drawn out manner. Near the end with one cat, I was stretching an 8oz cup of water and 1 small can of food throughout a 12 hour period, because that is all the cat could or would take. It was sufficient. She had vet checks regularly at that time, and the vet was satisfied she was getting enough and comfortable.
Not to upset you, but when a pet is unable to feed itself, they really don't have much time left. So you have to resolve to feed and water them on a schedule to ensure they are comfortable and hydrated. It is alot of work and stressful too.
They do get to a point where even if they "look" okay, they're not. They really do need you to do the work for them. As long as he's still taking food in this way, he will be fine. It's when you can't get them to eat and drink with a dropper etc. that you may have to start making some decisions for the well being of the pet. I have found most vets won't make that decision for you unless your pet seems to be in serious distress or is imminently at their end.
I'm sorry you are going through this. It is very difficult. As difficult as caring and doing hospice care for a dying human. Hang in there.