I'm so sorry to hear that you and your little baby are going through the emotional roller coaster of CRF. I just recently lost my 19 year old girl to it in September of this year. You are definitely not alone, and I would be more than happy to share some of the ideas that worked for Kiaira throughout her last few months.
First, I just want to mention that you can try different brands of kidney disease diets (Hills, Eukanuba, Medical etc.). It's ideal for a crf kitty be on a renal specific diet; however, I know that many don't like it...especially when their disease progresses.
Anyway, if different varieties aren't available where you are or your kitty still refuses it, it's more important (obviously) for him to eat than to worry about getting him to eat that specific food.
Once Kiaira's appetite started to decrease on a kidney specific diet, I heated her food up in the microwave every day in order to increase the smell and make it more appetizing. I also mixed that food with fancy feast (getting her to eat was more important) and she did quite well for a while.
We also tried a/d which can be purchased through your vet depending on where you live. I find that most animals really like a/d; however, depending on how icky your kitty feels due to having CRF, he still may not eat a substantial amount. You can also try heating that food too...I was heating everything I tired with Kiaira as I found it helped to some degree.
I also used Kitten food (development) from our clinic which was used to keep her weight from falling further. But before you start introducing different foods, speak to your vet as some foods and quick changes in an animal's diet can cause extreme GI upset.
Eventually, we got to a point when she had to be put on a fancy feast (and foods of that sort) diet as she refused to eat anything from our clinic. We also fed her cooked chicken, beef, fish, etc. along with her cat food everyday.
We also tried baby food which she liked; however, please speak to your vet before using it and make absolutely sure it doesn't contain onions (onion powder and/or salt) as it can cause anemia which is very serious.
Tuna juice, warm water, or a tiny amount of catnip sprinkled on her wet food were also things we tried with Kiaira, which seemed to help.
I don't know if this is something you would be interested in trying, but we also used Periactin which is an appetite stimulant. I know that it doesn't work for all cats; however, it seemed to work with Kiaira for a while. However, like with any medication, you should NEVER give it to your kitty without speaking to your vet first. A specific dose will be needed and there are side effects which will need to be explained and weighed. Furthermore, he/she may not think it's appropriate in you kitty's case.
Finally, we also raised her dishes in order to make eating more comfortable. We also talked to her and stroked her fur which will coax some kitty's to eat.
I'm sorry this post is so long, but I wanted to include everything I tried in hopes that you may find something here that works for you. There are also other great ideas (on kidney disease websites etc.) that didn't apply in Kiaira's case but may work for your kitty.
Dealing with renal disease/failure is emotionally difficult as will be the final decision to let your little loved one go. I had to make that decision before Kiaira got to a point where she couldn't do the things she loved. Please know that there is support out there during these difficult times. Take care and good luck with trying different things.