Leanne,
For just about any head strong pup where I am not seeing the results I like with a choke type collar, I switch to a Smith Wonder Lead . It's kind of hard to describe but it is made of a stiff ,springy cord similar to a lariat. It fits up snug right behind pup's ears and puts pressure right there. Sensitive spot , but it releases the minute you release tension or pup quits resisting.
Kinda concerned about his aggressive outbursts though. Dunno what that's about.