I am sorry your kitty is having trouble. Lip smacking is a sign of nausea, which goes hand in hand with kidney disease. There are anti-nausea medicines available that your vet can prescribe for your kitty which may be very helpful. A drug called reglan, also known as metoclopramide is a good choice. your vet can also get you a dose of pepcid ac which can help alot as well. A good potassium supplement is a must for a kidney kitty, and there is a gel called renakare which your vet can prescribe. Fluids may need to be administered under the skin several times a week, or even every day depending on how advanced your cats illness is. See the following website for more information on renal disease.
Kidney cats can be notoriously picky when it comes to food. This may be due to the nausea that they experience, or maybe they just aren't too crazy about the kidney specific diet. While it is ideal that your cat eat the kidney diet, it is more important that he eat something. If he detests the kidney diet to the point of not eating, he will need other foods and you will just have to do the best you can. If his current kidney diet is available in both dry and canned, offer both and see which he likes better. It is ok to supplement with other foods if needed.
I think a call to the vet for some pepcid and anti-nausea medicines are a good idea. Since you have been so compliant in having your kitty seen and having blood work done, your vet may not even require you bring your kitty in for an exam. However, if it has been more than 6 months since the last blood panel, your vet may want to pull some more blood to re-evaluate things. 1 year in a humans life is like 3 or 4 in a cats, so significant changes can occur in a relatively short period of time.
I hope that your kitty feels better soon, and that you'll let me know if I can be of further assistance. If this has been helpful, please hit the green accept button. Best of luck with your kitty.