I could agree on most points, but if you really don't see why a succesful man (even a true gentleman as the old James was) can be dragged down on a self-destructive spiralling after being fired and losing everything he has been building professionally for years, on a situation that only gets worse every time his perfect wife tries to help him because that good-wife behaviour only adds on to his own misery, because every time he sees her he can only see the succesful man he was not so long ago, and just because all of that he starts to feel resentment against her, confusing her well-intentioned attempts to support him with mere patronizing, if he actually feels like shit for being in that state but he just can't find anything else after months of trying, if he starts to feel like a burden to her... then I feel happy for you as it's obvious you've never being in such a delicate position. I was never there either, fortunately, but I don't need to see that neighbour to understand that finding a person who is in that very same position can make you feel better to the point to even forget who's the one who actually loves you (and who you actually love), as you feel this new one really understands you, unlike your perfect wife.
Alright, but then it creates the following problems in the game:
1) It makes the protagonist an unlikeable and probably unredeemable douchelord that any sensible person would have a hard time sympathizing with. Regardless of whether he was feeling that way or not, it's born out of miscommunication. One really needs to have their head up their ass if they blame their loving wife who not only tries to carry everything on her shoulders but also tries her best to give him moral support. None of what he blames Keeley for is her fault. He should've gone to a shrink to deal with his issues, not rebel against Keeley by hurting her even more to the point of doing revenge porn. Villains that you can't sympathize with make for bad protagonists. Even psychopath Light in Death Note that you hate with each passing episode can feel like a tragic character that one might even say was a victim of circumstances that would drive any person mad. James doesn't have good enough reason to feel like a tragic character deserving some level of human compassion. In fact, it makes you happier that Keeley found Claryce, and if that's the case, it just makes James feel like a glorified plot device to give Keeley freedom so she and Claryce can be together.
2) That connection that he shared with that neighbor is simply not in the game, otherwise, it might not only end up being a one-night stand that he never thinks about again, but it would make him develop a bit of a crush for her and create a conflict in him where he's torn apart by all the years spent with Keeley or the newfound excitement and sense of "pride and accomplishment" that this neighbor made him feel. But because we never see their chemistry, it makes it hard to try and put yourself into his shoes where you would be willing to find excuses for that cheating. I feel like a path where James would want to follow his heart and try to build a relationship with her would be more natural for that premise you described. I just don't see how he goes from sharing an intimate moment with a person who makes him feel valuable, to a desire to fuck as many random girls as possible. There's a missing link between point A and point B.
The point is there is no depth to James route because she didn't want to add depth to it. It's literally tacked on to keep a few people happy not aimed at being a full story to sink into.
Wouldn't it be better to do it by making it into a separate game altogether then and market it as a quick jerk-off material that doesn't have a trademark narrative? But because it's in the same game as Claryce's adventure, it all feels disjointed and his part reeks of lazy writing in comparison. Even if it's by design, it doesn't make for a good first impression. Knowing the BTS reasons for that is the only way to make sense of why it feels so odd.
Let's take GGGB into example. It also had some paths designed specifically for smut and non-stop crazy sex (like the Bimbo/Whore paths that I wasn't really into) which in contrast with Good Girl path felt very outrageous and crazy in tone, but the writing quality in all parts to me felt consistent (some landed better than the other of course), even if eventually those routes turn into a porn-fest without interesting story developments, the buildup and resolution are still there.
James' part in its entirety on the other hand feels like trolling because if we play the intended way and don't care about fixing things with Keeley, James gets a bad ending where an alternative good ending not featuring Keeley might've helped feeling better about the whole experience (similar to GtKC alternative ending that you get if you refuse to do what Christine asks of you). As it is, you only get a payoff if you DON'T play the intended way where James suddenly learns humility, but that realization feels too sudden and artificial. I wouldn't mind an ending where James finds new love with some girl that helps him feel like a man in the house again if that's what he truly desires. Or maybe he finally manages to deal with his issues and losing Keeley helps him grow as a person and understand his priorities. But if he does go out of his way to hurt Keeley more for his completely made-up reasons that have nothing to do with reality, then he deserves jail time for all I care.
I dismiss James because I don't like cheats, never have. Never saw the point of being with someone if you are going to sleep with other people, it puts people in a position to be hurt for no reason.
Is Jason dead to you as well since he kinda did the same to Elsa, even though she might not care enough about their relationship at this point and was the first one to compromise it by leaving and ghosting him? I also don't like cheats, but I love redemption stories. Where despite previous fuck-ups, a character still deserves to have a chance and find happiness as long as they strive to do the right thing in the end. This is why Chloe is my second favorite character after all (Xara takes the cake) and her sins were much more serious than simply breaking someone's heart, but I was still rooting for her to get rid of her abusive father and find happiness with Paul instead of going to prison for being the accomplice in blackmail, murder, and even terrorist attacks.
I feel like relationships are not really tested unless you end up in a situation where you're tempted to just forget about monogamy for one moment and enjoy the primal ways of our promiscuous ancestors. And some people just don't have the iron will to resist that temptation and fail that test. But how they deal with this afterward is what matters. I know some couples that only got stronger because of that first cheating mistake because it helped them realize that their love for their partner is much stronger and more important that no immediate pleasures would make it worth losing their soulmate. In some instances, the other half doesn't even know about the cheating that happened, but as long as they closed off that chapter in their life and are dedicated to making their partner feel loved and cared for, then I don't personally see the need to expose them and ruin their happy relationship because they're not the same people that they were at the moment of the cheating. And sometimes, even in examples where cheating leads to a breakup, people can grow from this experience and properly cherish their next relationship.