I agree with Jcat, this is normal Kitten behavior. I went through this with my now 1.5 year old cat Cerce (see avatar). He doesn’t sound like he’s being aggressive, he’s just playing around and exploring. Remember you’ve got a tiny apex predator in your home. Kittens want to play all the time. They play and play and play until they suddenly fall asleep. Most don’t want to sit still and be petted for long periods of time yet I think it’s really cute. Instead of using string, I would throw things at him and play fetch. Crumpled up pieced of paper, small balls, and little stuffed mice you can get in any pet store were Cerce’s favorite. (now she LOVEs yarn, but the kitten is too young and might eat the string). Laser pointers and cat dancers also provide hours of entertainment for your kitten and should tire him out.
What your doing to teach him right from wrong seems ok. Also, After you scruff him, gently push him down to the ground and say “no” that’s what Mama cat would do. Also distract him by throwing a toy.
(see: http://cats.about.com/od/behaviortraining/ht/ScruffingCat.htm)
They also like to climb. Since they can’t jump high yet, they’ll use their claws to climb your legs. Definitely wear long, thick pants for now. Also trim his nails with special “cat nail clippers.” Don’t cut them too short though, don’t hit the “quick”, just the sharp tips. If you can’t do it yourself (may require 2 people), then you can get a vet to do this for a small fee. That’s what my sister does for her cat. It helps if you can do it when his relatively calm and tired out. And obviously scratching posts are a most. The cheap cardboard ones are fine.
Good luck! I think with these tips you’ll be able to stem his behavior.