When it comes to how young Ezra was, I think about how young kanan was when he fought in the clone wars, how Hera has been implied to have been a rebel for a very long time, how Sabine is treated as a mandalorian, and I wouldn’t think it out of the picture to imagine that zeb since he was prominent in the honor guard of the royal family of his whole planet was probably was prepared from a young age for that too. They probably all see something of themselves in him.