I know you mentioned that the kitten seems to like the cold hard floor the best to lay on. It might be better to put a heating pad under a towel set on the lowest setting for the kitten to lay on. It probably doesnt have any body fat or resourses to keep itself warm right now. Also, for kittens I've rescued at night with no kitten formula available until morning, I run to the store and get a small can of either lactose-intolerant milk, or lactose-intolerant baby formula. The kitten doesnt have the enzyme to properly digest the sugar found in cow's milk, but these will get it through the night. Also, if it's too weak to suck a nipple, carefully hold the kitten up right on your chest, holding it head up, and drip a tiny bit at a time on the end of it's tongue and gently tickle around it's tail. This will stimulate it's suck reflex. Be very careful it doesnt get any of it in it's lungs.