Re: Licking behavior?
Are those items he is licking "rusty" at all? I had a cat who was anemic, and my first clue, was she was licking the rusted bottom door of an ancient farm-kitchen sink of the home we were renting. Licking metal items can sometimes indicate a mineral deficiency.
My best suggestion would be a vet visit, specifically for a blood test to help the vet determine if the cat is deficient in any nutritional and/or developmental areas of their body/diet.
Best of luck,