@saudagarbeta
From what I noticed in these Manhwa’s based around a similar culture/era/period the husband and wife usually have their own quarters, so that’s probably why they don’t sleep in the same room. I guess makes it easier to make the characters have distance, secrets (like affairs lol) and etc. Kinda like how there is an emperor, empress (emperor’s “wife”) and then also a queen (which is also a “wife”, mistress, concubine, w/e).
IMO, I believe he put distance between Lex and her, because he already considered her his wife (since they’re married and he’s aware) so he wants her to love him and not some facade character that isn’t him. If you recall in previous chapters in the beginning where I guess she wasn’t aware that he known of her existence, he did talk about his wife and told others about her and didn’t go after women because of her.