Rebecca: the proposal and the red flags

Very suddenly, to the narrator of Rebecca as well as the readers, Maxim de Winter proposes. Everyone’s shocked. 
The characters meet in Monte Carlo. Mrs Van Hopper, out of the blue, decides to go to New York. The day before the trip, the narrator cannot see de Winter because he’s away, so on the last day, she runs to his room to say goodbye. He tells her to follow as he comes down to breakfast, then gives her the choice between going to New York with her employer and going to Manderley with him. 
He proposes to her, you little fool. 

“This sudden talk of marriage bewildered me, even shocked me I think. It was as though the King asked one. It did not even ring true. And he went on eating his marmalade as though everything were natural. In books men knelt to women, and it would be moonlight. Not as breakfast, not like this.” (Ch.6) 

The proposal scene is vivid. And full of red flags. 
Readers like me, female, and having read Jane Austen and bad marriage novels, are quick to notice the bad signs. Before this scene, there are already a few, mostly Maxim de Winter’s sudden change of moods, and lack of openness, also his condescending tone to the narrator sometimes. 
There are a few others in the proposal scene: the curt response, like an order (“Shut the door”); the way he goes on with his things without explaining and makes her wait, even though she says she has to go back to Mrs Van Hopper; the way he asks her to marry him; the unromantic, even cold, tone; the choice of words such as “ignorant”, “little fool”, “unintelligent”; the line “philanthropy is not my strongest quality”; the laugh; the line “your duties will be almost exactly the same”. 
The worst red flag? 

“And he took an emery board out of his pocket and began filing his nails.” (ibid.)

What kind of weirdo is this? Or is it standard for a man in this time period to have an emery board in his pocket?