Well this thread is completely derailed.
As I already stated in an earlier post, I can't let him outside because I'm in a 3rd floor apartment in the middle of the city, and I can't shut any doors because I have a one-room apartment. So none of that is an issue in this case.
I tried the stuffed dog but he's terrified of it. On the other hand, if he starts attacking me all I have to do is wave the dog at him and he takes off and hides on the other side of the room. On the other other hand, I feel bad for scaring him.
I talked to a friend of mine tonight who is a cat lady like me, and she suggested the water gun. I guess maybe I'll start looking for one, just to use when he's really out of control. She told me that he won't become less affectionate as long as I'm sure to cuddle him as soon as he stops the inappropriate behavior.
She also said that even though he's only 4 months, he might already be at the age to be neutered. His pee is starting to smell really terrible, and it looks like his testicles are dropping. I guess I have to make an appointment with a vet and get a friend to come translate for me.
EDIT: And yes, he has three scratching posts and a mountain of toys, and I give him new ones all the time (made from trash, scraps, etc.) which he loves. But not as much as he loves slicing me open. In fact just a moment ago he dug his claw so deep into my finger that he couldn't get it back out again for several excruciating seconds.