I always assumed that Bob was just a massive asshole to her off-camera where we don't see him doing things that justify her behavior. Given my own experiences with men, it's so plausible I just never questioned it. It's definitely a weakness of the script that we don't really see Bob actually do anything to justify Linda's rage at him, aside from not being able to satisfy her sexually anymore.
(Funny story, as soon as I met Zuri, the Hot Secretary, my first thought was "Ah, that explains it, I know where this is going now." But then that just never happened.)
I always assumed that before the game happened, we know that Linda was developing feelings for the MC, for whatever reason. At the same time, she was losing interest in Bob, both as a husband AND as a sexual partner. What we see during the game is him continuing to get his without caring if she's being satisfied, to the point where she just eventually gets annoyed with him sticking his dick in her while she's trying to go to sleep or reading. Basically, the relationship just isn't there anymore for her and he's not seeing the obvious clues. She knows what she is feeling is "wrong", and that comes out in the game. It doesn't mean that she's suddenly going to find Bob sexually attractive again because what she's feeling is wrong.
Both Bob and her are professionals, but unless you tell Zuri/Suri the truth all the time, Bob's company should be making bank. We can tell that [Spoilers for 5] she still somewhat cares about Bob by her reaction to getting caught (if you choose that route). I'd just say that she's heavily conflicted about her feelings for the MC, her caring about Bob, the societal norms, and her wanting everything to proceed further at home with the girls before anything comes out and can destroy the home. In all honesty, near the end of 5, I would have expected someone in her position to be seeing a divorce attorney regularly and be preparing the paperwork. Bob's lost in it all, but that has quite a bit to do with his lack of attention at home and his lack of attention to what his wife wants.