What works for one cat may not work for another so try something else than a water bottle. It’s obviously not working and anything you could put in the water would likely be far too harsh. I mean if you are spraying it in his face it’s also going into his eyes and you don’t want to trade dealing with a fairly typical minor problem for an emergency visit to the vet.
I’ve been goiing through the same thing with mine for the last several months. This is very normal behavior for kittens. He regards you as a member of his family and is playing with you the exact same way as he did with his siblings and Momma cat. He just doesn’t realize that you cant take the same degree of biting and scratching as another cat can. There are several other things you can try to educate him to this reality. Firstly, don’t let him get away with it without letting him know in no uncertain terms that this is not acceptable. Cats don’t obey commands the way dogs do, but they are very intelligent and are sensitive to the tone of your voice. A very loud OUCH or similar sounds go a long way. Mine still lies in wait to ambush my feet, but she now does it with soft paws——claws retracted. Every once in a while she forgets herself and I have to remind her with a loud ouch, stop it!!
The other thing I did in the beginning was that everytime she bit or scratched it was off into the bathroom for a five min. time out. This takes all the fun out of it. They are playing with us because they enjoy interacting with us.
The other thing I did if she was biting my hands was to grab her by the scruff firmly but not harshly, look straight into her face and said—-STOP IT—and promptly tossed her off the bed. It got the point across. (Just keep in mind that you shouldn’t hold them up by the scruff of the neck which could be damaging——this is more for when seated on the couch or bed.) Again, she was deprived of fun interaction for the next few mins. Then afterwards I would get out one of her toys and play chase with her. This way she got it out on the toy. Eventually she realized that human hands and feet are not cat toys——human hands HOLD the cat toys.
It’s really kind of comical now when she starts to bite my hand——I just go uh, uh, uh in a warning tone and she freezes in mid-bite with her mouth agape and then just a little nibble or a lick.
For the pencil erasers, the only thing I can suggest is to keep them upside down in the holder so the eraser end isn’t available for chewing. That’s also what we have to do with any inappropriate objects for chewing——it’s kind of like baby-proofing the house.
Mine is currently fascinated by the ends of my reading glasses so I just have to keep remembering to fold them up so the “delicious” part is inaccessible.
You just have to keep trying diferent things to see what works for your cat. There will be many other bits of advice offered and just keep experimenting.