I know what you mean about the answering back! He often steps back from me when I tell him off and does one of his small barks and raises his paw at me! Like I say though, he soon moves on.
Haha, this is exactly what Millie does, we really have to try to not laugh at her.
We have tried everything to stop her biting and the only method that seems to work for us is ignoring her. As people have previously mentioned, hen she bites just say 'ow!' or a firm 'no!' But immediately get up and walk out of the room. As we have a slightly open plan layout we walk in to the kitchen, turn our back to her and cross our arms. My partner and I both get up even if she has just tried biting one of us. We don't go back in to the other room until she has either sat down behind us calmly or if she goes back in to the lounge and lays down, this usually only takes about 30 seconds then we carry on as normal.
I created a thread similar to this one only a matter of days ago so I am far from an expert! Just hang in there and be consistent, the members on here are very helpful and have some great advice and support.
By the way, any pictures of your pup?