re: the licking and chewing. He could possibly have ringworm. He was out and about for a while. Is there missing fur in that area?
Also, it's best to take the little mister to the vet and get him de-wormed, as most wild cats have them, because of fleas, and get him a general check up. I'd recommend getting him an FIV and feline leukemia test as well, since that is standard when getting a new kitty and you don't know where they have come from. (Especially if you have other cats in the house, as both of those are contagious, through saliva and using the same box. Very different than the human versions of the diseases.) Also, he will need a panel of shots. He probably won't need rabies, since I'm assuming he will be an indoor cat, but I think there are several other vaccines he needs to get.
If he does indeed have ringworm, you will have the glorious task of doing all of your laundry and de-fungusing the house. Fortunately that shouldn't be too hard since you said everything is plastic, but all bedding, both yours and his, will need to be laundered in hot water, and the carpets will need to be done.
And... most likely, the vet will give you some awful shampoo that you will have to bathe the cat with, but there is a better way. The flea control product called Program can be used to cure ringworm. You buy the dosage that is appropriate for your cat's weight, and give him double the dose. Then repeat in a few weeks. (I'm not sure how many, but I can check.) Better than having to wash your cat every day.
I agree with the neutering thing, when he is old enough to get it. (I think they can get it pretty young now.) It's either that or having him mark his territory when he's older by spraying cat piss all over the walls and your things. And trust me, once a cat pisses on something, it's best to just throw it away, because you will never get the smell out, no matter how many times you wash it.