Well, I haven't read the book your referring to, so I might not be much help here.

I think our habitual behaviors are what makes up our identity. A thought and feeling can be fleeting as well as some actions. Thoughts lead to feelings, feelings lead to actions, actions lead to behavior.

I think you can be aware of the fact that you act differently in different situations. Many people have a home life and work life deviations.

Your authentic self is not necessarily one in which you are honest, but more like the one that is most aligned with your feelings and thoughts. It's who are when you are with your closest friends/family. Or who you are when no one is around.

Your personality is just all the characteristics that make you unique. It's who you are and how you behave.