Hey Akari:
I have had some cats that like to play rough and they pretty much grew out of it as they got a little older. Although every one of the cats that liked to take a swat at someone walking by usually had that habit until the day they died. Lol IMO it is tempting to play rough with them when they do it, but it only contributes to the problem.
I would suggest not scratching him too much in the places that seem to excite him, always play gentle with him, and when he gets excited from scratching or begins to play rough just stop interacting with him; send him away from you if necessary. I would also not scratch or play with him for a longer period of time when he behaves this way. Instead of a couple minutes try 10 or 15.
Kittens and young cats have an abundance of energy and it sounds like you have provided plenty of toys for him, you give him attention, and most importantly Bentley gives him attention! It has been my experience as they mature they tend to become gentler. Maybe someone else will have some better advice for you but this is all I got for you. 🙂
