How does behaviour of Offred and the Commander show that their relationship progressed in Chapter 29?

In Chapter 29 it is evident that Offred and Commander's relationship has progressed. They're relaxed in each other's company, they leisurely play games of Scrabble, and Offred is even allowed to secretly read in his company (something she considers better than sex).

They are so relaxed, that Offred even goes as far as to ask for conversation rather than the forbidden book. The Commander even shares personal information with her, and she feels free enough to ask him things she shouldn't. She even pens a phrase, feeling the lost power of words as she writes, "Nolite te bastardes carborundorum."

The Commander has learned to care for Offred. He wants her to live a bearable existence with some form normalcy. He "want[s] [her] life to be bearable to [her]" (29.54) He most certainly doesn't want her to die as her predecessor had, and she knows that because of this she holds a little power over the man who has the power to make a difference in her life.