my pup is 7 months and she was acting similar. I had tried the "choke chain" but she would pull just like yours and not care that it was tightening. We moved to using a prong collar and and after about a minute of introducing it to her she was back on track. Walking on leash nicely. sitting when stopping. no longer lunging after rabbits and squirrels. and in the house. i would keep her on leash with the collar on inside and after a few corrections, she was awesome. check this video out. i thought it was pretty helpful in starting.
That's perfect, thank you! After read your post I remember my trainer saying to use a prong collar if the chain alone wasn't enough. Hallelujah, this might be a life saver lol.